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In this paper, an active electromagnetic interference (EMI) choke for both common-mode (CM) and differential-mode (DM) noise suppression is proposed. Three isolated windings with a different number of turns are wound on the same magnetic core. One of the windings is served as the auxiliary winding connecting to an active circuit called the negative impedance circuit. The inductance of the EMI choke is substantially boosted up to effectively attenuate the low-frequency noise. This technique leads to a greater inductance but fewer turns and smaller size of the EMI choke. Different from the design of a conventional EMI filter, which uses separated CM and DM chokes, this proposal saves the cost and space of the EMI filter. The enhancement to the CM and DM impedance is individually analyzed and experimentally confirmed. Based on the classical CM and DM noise models, CM and DM noise insertion losses are predicted using computer simulation. The simulation results are validated by a network impedance analyzer. Finally, conducted EMI tests are carried out to verify the effectiveness of the proposed technique. [ABSTRACT FROM PUBLISHER]

Electronic products consist of parasitic capacitance between the circuit components and the ground, which introduces common mode (CM) noise. A CM inductor is used to block the noise following into the power supply affecting the others. However, the CM inductor and the parasitic capacitance could create resonance phenomenon that affect the filter performance in low frequency. In this paper, we investigate into this resonance phenomenon by giving a detailed analysis of the CM inductor and filter configuration. A three-winding CM inductor is then proposed to solve the aforementioned problem. This three-winding CM inductor consists of two traditional CM inductor winding and an auxiliary winding connecting to a negative impedance converter. The impedance of the CM inductor is virtually boosted up. Without physically increasing the value of the inductance, the noise attenuation in low frequency is improved and the resonance phenomenon is significantly mitigated. A prototype is constructed and practically tested on a 100-W switched-mode power supply. Experimental results show that the three-winding CM inductor operates as theoretically anticipated. The noise level at the resonant frequency is reduced by 21 dB, whereas the power consumption of the additional circuit only consumes 0.5 W. [ABSTRACT FROM AUTHOR]

This paper proposes a phase-shift interleaving control method for variable-phase switched-capacitor (SC) converters that can perform voltage conversions with little electromagnetic interference over a wide range of operating condition. This is achieved by having multiple units of SC converter connected in parallel and an N-state hysteresis unit selection control scheme which works along the interleaving control to vary the number of converters in operation. By having the capacitors of inactive units connected to the output and the converters operating with output interleaving operation, the output capacitor that is typically required in SC converters for maintaining a small voltage ripple is made redundant in this configuration. A three-unit SC converter of the proposed configuration is described in this paper. Experimental results show that the proposed solution works satisfactorily with good regulation, input and output interleaving operations, and dynamic response for a wide operating range. [ABSTRACT FROM PUBLISHER]

The switched-capacitor (SC) converters are ideal switching-mode power supplies for consumer portable electronic devices due to their nature of being light weight, small size, and high-power density. However, they suffer from a discontinuous input-current waveform with large di/dt, which leads to significant electromagnetic interference emission. This paper proposes a configuration of SC converters connected in parallel, with their inputs and outputs interleaved and adaptively controlled. The interleaving operation is performed by using an original type of control in which both the capacitors’ charging time TON and switching frequency are adjusted to get the line and load regulation. It is shown that, for a given range of variation of the supply voltage and load, there always exists a solution [TON, TS] that assures both output-voltage regulation and perfect interleaving. Experimental results are provided to validate the feasibility of the proposed scheme. Precise interleaving, and good line and load regulation are maintained for all the designated range, including the transient periods. [ABSTRACT FROM PUBLISHER]