2,884 research outputs found
A Closed Loop Delay Compensation Technique to Mitigate the Common Mode Conducted Emissions of Bipolar PWM Switched Circuits
This paper presents the design of a new closed loop technique that reduces the common mode conducted emission. This technique can be applied to all switching circuits in which couples of outputs are modulated by a bipolar PWM signal. It is based on the compensation of the delay between complementary output switching edges, using a simple sensing circuit and a low computational effort software algorithm, which is implemented in a microcontroller driving the switching circuit. One of the main advantages of the proposed technique is the reduction of the disturbance energy, without affecting the system efficiency. The technique is practical to implement, and the measurements performed on a power inverter prototype confirm the theoretical analysis outcomes about the reduction of the conducted emission in the lower-to-medium frequency range
Investigation on the Susceptibility to EMI of Second-Order ĪĪ£ Modulators
This paper analyzes the effects of radio frequency interference
on second order ĪĪ£ modulators based on continuoustime
(CT) and on discrete-time (DT) architectures. Specifically,
Modulators used for the acquisition of sensor signals are targeted,
which can operate with moderate clock rates due to the relatively
small bandwidth of the signal to be acquired. A continuous
wave interference with frequency above that of the modulator
clock signal is superimposed onto the nominal input one with
the purpose of evaluating the degradation of their performance,
and more specifically their capability to demodulate out of band
interference
An Adaptive Method to Reduce Undershoots and Overshoots in Power Switching Transistors Through a Low Complexity Active Gate Driver
Active gate drivers lend themselves well to reducing over- and under- voltages during the commutations of hard switched power transistors, as well as to damping resonances. However, their control strategy is a major challenge, as it should account for variations of operating condition, parameter spread, and non linearities of the driven transistor. This paper proposes an effective control method to reduce overshoots and undershoots in a power transistor driven by an active gate driver. The modulation pattern is modified on-the-fly and none a-priori characterization is required. The presented method modifies the timing parameter to attain almost zero over- and under- voltages with the lowest power losses. This is achieved by combining a low complexity active gate driver with the measurements of peak values of the drain-source voltage. The technique was experimentally assessed for a 48-12 V DC-DC converter, and resulted in better switching performance than standard solutions and open loop control
Investigations on the Use of the Power Transistor Source Inductance to Mitigate the Electromagnetic Emission of Switching Power Circuits
With power designers always demanding for faster power switches, electromagnetic interference has become an issue of primary concern. As known, the commutation of power transistors is the main cause of the electromagnetic noise, which can be worsened by the presence of unwanted oscillations superimposed onto the switching waveforms. This work proposes a solution to mitigate the oscillations caused by the turn-on of a power transistor by exploiting its source inductance plus an external one. In this context, an optimization method is proposed to find the optimal value of the source inductance as a trade-off between oscillation damping and power dissipation. The experimental results performed on a prototyped power converter assess the proposed technique as the spectrum of the conducted emission is attenuated by 20 dB at the oscillation frequency. With respect to traditional solution based on snubbers, the proposed solution results in a similar oscillation damping, but with a 0.5% higher power efficiency
A SPICE model of Operational Amplifiers for Electromagnetic Compatibility Analysis
This article proposes a macromodel to predict the nonlinear behavior of operational amplifiers having their baseband
signal affected by out-of-band disturbances, such as those caused by electromagnetic interference. Like any opamp macromodel,
the one proposed in this work was developed with the purpose of not sharing neither the technology parameters nor the circuit
topology of the real device. Besides the baseband macromodel, the proposed solution comprises a high frequency equivalent circuit
that propagates the out-of-band signals, and a nonlinear model to account for their demodulation. The proposed solution is suitable
for any SPICE-like simulator. It does not affect the simulation performance, meaning the simulation time, the simulation accuracy
and it does not cause any convergence issue. This article shows in detail the macromodel, the method to calculate its parameters as
well as its experimental validation, which was obtained comparing the model predictions with the results of the measurements carried
out on a commercial device
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