Spread-spectrum (SS)-based pulsewidth modulation (PWM) techniques play an important role when tackling the electromagnetic interference (EMI) problem in the switch-mode power supply (SMPS) domain. They achieve the best EMI noise reduction and emerge as a promising and very effective solution to comply with electromagnetic standards. The current work provides an insight into the SS techniques: its history, its types, and mainly its ability to mitigate the EMI problem in the SMPS domain. Moreover, it gives a short review of the different SS-based PWM techniques going from the most basic and simple, i.e., the periodic modulation, to the most developed and complex, i.e., the random and chaotic modulations. Besides, a short review of the different implementation methods was addressed and they were categorized into analog and digital implementation techniques where its pros and cons were provided. Finally, a new fast digital implementation method based on a dsPIC33F microcontroller is presented. Its effectiveness was proved and its advantages over the reviewed implementation techniques were recognized. It reached a 20 dBuV EMI level reduction when the digital chaotic and periodic profiles were embedded into a boost converter prototype.

A Review of Spread-Spectrum-Based PWM Techniques—A Novel Fast Digital Implementation

Forward DC/DC converters are widely used in low and medium power circuits that are widely used in the aerospace and navigation fields Power converters are usually sources of electromagnetic interference (EMI), which is due to their higher voltage and current transients The traditional method is to add expensive filters on the primary side or the secondary side, but its disadvantages are high cost and poor adjustability Based on the principle that the greater the number of derivations of voltage transients, the lower the high frequency electromagnetic interference contained in this voltage, a signal containing small high-frequency noise that is suitable for the hardware circuit as a reference signal is selected, and a closed-loop gate drive method is used in this paper, which attenuate the conducted EMI noise in the input bus of the forward DC/DC converter The reference signal shapes the output signal to achieve the purpose of suppressing electromagnetic interference through the closed loop circuit The advantages of this method are making the output highly adjustable, reducing hardware size and weight and lower cost compared with filter method Compared with the method of controlling current to reduce electromagnetic interference, the proposed method is easier to implement Firstly, the relationship between the derivative order of voltage transient and electromagnetic interference is introduced Secondly, the experimental principle of single-ended forward circuit controlled by closed loop is introduced Simulation and experimental results show that the proposed method can achieve voltage shaping and suppression of voltage overshoot effectively Compared with the traditional hard-switching control method, the proposed method can make the high-frequency components of the drain-source voltage of the primary-side MOS transistor and the secondary-side output voltage have a greater attenuation

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Closed-Loop Gate Drive for Single-Ended Forward Converter to Reduce Conducted EMI

In this paper, a hybrid PWM modulation method is proposed to reduce the EMI filter size of GaN based inverters. Time-based PWM modulation and frequency-based modulation methods are combined to achieve a reduced EMI profile, which reduces the filter size required to meet EMI standards. An EMI test bed based on the CISPR EMI standard is built using a 10-kW GaN inverter and modeled using LTspice simulation. The simulation model parameters were finely tuned to represent the actual system. Experimental EMI tests were conducted to verify the simulation model. The hybrid method is simulated and tested achieving an attenuation of 7-12 dBs. It is shown that this method reduces the EMI filter size by 21% which helps to increases the power density of the inverter.

A Hybrid PWM Modulation for EMI Filter Size Reduction in a 10 kW GaN-Based Three Phase Inverter

Switch mode power converters are site of electromagnetic interference (EMI) issues that decrease their performances and deteriorate their electromagnetic environment and stability. Thereby electromagnetic compatibility (EMC) plays an increasingly important role to guarantee a correct functioning of DC/DC power converters and to ensure reliability throughout their lifetime. In this paper, the chaotic pulse width modulation scheme based on logistic map (LPWM) was used to mitigate EMI. In fact the LPWM is a spread spectrum technique that spreads out uniformly the entire energy over the frequency band. In the current work, the LPWM scheme has been benchmarked against the traditional PWM and by means of LTspice simulations it has been shown out the great extent of EMI reduction.

Electromagnetic interference reduction in boost converter using logistic PWM

Based on the advantages of the chaotic spread-spectrum technique and the soft switching technique, this paper proposes an effective technique to improve the electromagnetic compatibility (EMC) of the converter. Firstly this paper designs a chaotic soft switching converter. Then it is proved by mathematical derivation that the chaotic soft switching technique can be more effectively in suppressing the electromagnetic interference (EMI) of the converter. In this paper, we derivate the mathematical expressions of the spectrum of the power transistor's drain-source current, which work in the PWM mode, the soft switching mode, the chaotic spread-spectrum mode and the chaotic soft switching mode respectively. Finally, the simulation experiment is carried out, and the spectrum of the power transistor's drain-source current is obtained. The results show that the chaotic soft switching converter has better EMC performance.

Study on chaotic soft switching forward converter

Boost converter is most widely used DC-DC converter for renewable energy applications. The operation of high frequency switching DC-DC converters causes Electro Magnetic Interference (EMI), which is degrading the normal operation of the converter and other adjacent systems. Therefore power converters must comply with the Electro Magnetic Compatibility standards in order to ensure the proper operation of converters and not to pollute the nearby systems. This paper discusses an integrated conducted EMI suppression approach, the chaotic soft switching technique based on Field Programmable Gate Array (FPGA) technology to provide a significant EMI noise attenuation in solar fed DC-DC boost converter. The solar fed DCDC boost converter is designed, simulated and implemented in hardware. The results obtained and the FFT analysis are strongly substantiate the proposed approach. The obtained results also compared with the traditional DC-DC boost converter results. The proposed system may replace the bulky passive EMI filters wherein which the space is the major concern.

Sudhakar N

Papers

FPGA based Chaotic PWM combined with soft switching for effective EMI mitigation in boost converter