Thorough Study of Multi-Switching-Frequency-Based Spread-Spectrum Technique for Suppression of Conducted Emissions from Wireless Battery Chargers

Abstract

The multi-switching-frequency technique is one of the spread-spectrum techniques for suppression of conducted emissions generated by wireless battery chargers. Its advantage is a relatively easy implementation with a microcontroller. In this paper, an original thorough experimental study of the effect of the multi-switching-frequency-based spread spectrum technique parameters (e.g., combinations of number of pulses, frequency order, etc.) on the performance characteristics (conducted emissions levels, efficiency, etc.) of an inductive-resonant wireless battery charger with a closed loop control is presented. It is shown that combinations of a number of pulses and frequency order have a noticeable impact on the performance characteristics of the wireless chargers. The suppression of the conducted emissions can be improved significantly by using optimized parameters of the technique. Moreover, it is proved experimentally that a relatively inexpensive microcontroller with a transceiver can be used to implement both closed-loop control of the wireless charger and the multi-switching-frequency technique.

Dynamic Resonant-Inductive Wireless Power Transfer System for Automated Guided Vehicles with Reduced Number of Position Sensors

“…Therefore, at lower coupling coefficients, the motor's rotating speed was maximum, but at higher coupling coefficients, it was minimum. These phenomena can be described by the fact that approximate output voltage of a resonant-inductive WPT system with seriesseries compensation is inversely proportional to the mutual inductance (and therefore, the coupling coefficient) between the transmitting coil and the receiving coil when the dynamic WPT system operates at the resonant frequency or near it [16]. Therefore, at lower inductive couplings, the output voltage of the resonant-inductive WPT system is higher.…”

Wireless Battery Chargers Operating at Multiple Switching Frequencies with Improved Performance

“…When designing a wireless battery charger, electromagnetic compatibility (EMC) issues should also be considered, because they are significant sources of conducted and radiated electromagnetic interference (EMI) to sensitive electronic devices [5][6][7][8][9][10], as is depicted in Figure 1a. Therefore, different national or international EMC standards specify the limits and measurement methods of EMI of the wireless battery chargers.…”

“…One of the drawbacks of the multi-switching frequency technique (as well as the other spread-spectrum techniques) is that the peak value of coil currents may increase significantly [9]. Another drawback of the technique is that EMI reduction is only moderate (up to 8.3 dB for the conducted EMI (if the standard 9 kHz resolution bandwidth of a spectrum analyzer is used) [9] and up to 4 dB for the radiated EMI (if the close-tostandard 10 kHz resolution bandwidth of a spectrum analyzer is used) [5]). Higher EMI reduction can still be achieved with the multi-switching frequency technique, if a higher number of frequencies are used, but this would inevitably lead to a larger difference between the minimum and maximum switching frequencies Δf and it would result in a higher drop in the efficiency in CC mode (at lower value of the equivalent input resistance of a ba ery) and a more significant increase in the peak and RMS values of currents of power components of the wireless ba ery charger [9].…”

“…Although less effective (in terms of EMI suppression), the spread-spectrum approach has gained substantial popularity over the last two decades because it can be used for suppressing conducted and radiated EMI simultaneously and can be implemented by using a suitable program code for a microcontroller. The spread-spectrum technique was initially used for the suppression of EMI from traditional switching power converters [11,12], and recently, it was applied to inductive-resonant WPT systems (including wireless battery chargers) [5,[7][8][9]. Several types of the spread-spectrum technique exist for EMI reduction from wireless battery chargers, but the multi-switching frequency technique is preferable to other spread-spectrum techniques for wireless battery chargers because it can be implemented by using a relatively inexpensive microcontroller that can be used simultaneously for implementing constant current (CC) or constant voltage (CV) battery charging modes [9].…”

“…The spread-spectrum technique was initially used for the suppression of EMI from traditional switching power converters [11,12], and recently, it was applied to inductive-resonant WPT systems (including wireless battery chargers) [5,[7][8][9]. Several types of the spread-spectrum technique exist for EMI reduction from wireless battery chargers, but the multi-switching frequency technique is preferable to other spread-spectrum techniques for wireless battery chargers because it can be implemented by using a relatively inexpensive microcontroller that can be used simultaneously for implementing constant current (CC) or constant voltage (CV) battery charging modes [9]. One of the drawbacks of the multi-switching frequency technique (as well as the other spread-spectrum techniques) is that the peak value of coil currents may increase significantly [9].…”