Analysis of Common Mode Noise in Floating Boost DC-DC Converters
Output-floating DC-DC converters are widely studied in new energy fields such as photovoltaics,fuel cells,and energy storage systems due to their high voltage gain.Taking the output-floating Boost DC-DC converter as the research object,this paper deeply analyzed the mechanism of common mode conducted noises and derived an equivalent model considering circuit parasitic parameters.Under the premise of adding a linear impedance stable network on the input side,the working mode analysis of four boost circuit topologies shows that the output-floating topology structure has three more high dv/dt nodes in the circuit compared to the input-output static point connection structure.With the switching state of the converter,the common mode noise current corresponding to these high dv/dt nodes can generate the common mode noise current flowing towards the ground on the flow path.A model of an output-floating Boost circuit topology was established,taking into account the equivalent series resistance and equivalent series inductance of the input and output capacitors of the converter,as well as the parasitic capacitance of the switching transistor.Based on the substitution theorem and Kirchhoff voltage law,a common mode noise model for an output-floating Boost converter was derived by equivalently replacing a normally operating device containing parasitic parameters with voltage and current sources of the same waveform.At the same time,using the superposition theorem,the common mode noise model was simplified by considering a single noise voltage or current source.Based on Kirchhoff's current law,the common mode noise acoustic current flowing through the parasitic capacitance of each converter node under the action of a single noise source and the total mode noise current on the linear impedance stable network sampling resistor were derived.Four experimental prototypes with a rated power of 48 W were built.The output voltage,inductance current,and driving voltage were tested under 24 V input voltage working conditions.In a testing environment where common mode interference was conducted,four prototypes were tested.The common mode noise spectra were obtained through EMI receivers.It was found that the common mode noise of Boost topologies A and B is consistent in the low-frequency range and differs by 5 dBμV to 10 dBμV in the high-frequency range.The common mode noise spectra of boost topologies C and D are consistent in the 0.15 MHz to 0.5 MHz range.In the range of 0.5 MHz to 5 MHz,the common mode noise spectrum of Boost topology C is slightly higher than that of Boost topology D.The average value of the common mode noise spectra of Boost topologies C and D remains at the same level in the test frequency range of 5 MHz to 30 MHz.The common mode noise of Boost topology D is increased by approximately 12 dBμV compared to Boost topology A.Therefore,traditional input and output stationary point connected Boost converters have better common mode noise characteristics,while output-floating Boost DC-DC converters have high common mode noise limitations.
Common mode noiseoutput-floating converterequivalent modelparasitic parameters
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