Enhancements of the Multiple Input Buck Converter for

Enhancements of the Multiple Input Buck Converter for Envelope Tracking Applications P. Fernández Buck derived converters operating in open loop can improve its dynamic response by using higher order output filters. The MIBuck with 4 th order Bessel filter is presented here. A multiphase MIBuck is also proposed. Experimental results are shown. Why 4 th order Bessel? Mission of the output filter in ET: Grupo de Sistemas Electrónica de Alimentación § Reject the switching frequency. Keep waveform. ¢ Bessel filter has flat pass-band flat groupdelay. Design Hints: § Filter adapted to the Switching Network Impedance § Guarantee CCM § Switching frequency rejection (40 d. B) Angular switching frequency for 40 d. B Rejection Boundary angular switching frequency for MCC 4 th ORDER MIBuck § fs = 4 MHz fcutt-off= 1 MHz 4 th ORDER Multiphase MIBuck § fs = 4 MHz fcutt-off= 2 MHz § Multiphase operation introduces a notch at the switching frequency, so the cutt-off frequency of the filter can be increased with less switching noise CONCLUSIONS The use of a higher order Bessel output filter can yield a significant improvement in the slew rate and bandwidth of the MIBuck converter. A multiphase configuration has been demonstrated to further improve the capabilities of this converter for ET applications. The former MIBuck presents a slew rate around 6 V/ s. By properly designing the filter means multiplying by 3 the slew rate and up to 4 times in the Multiphase MIBuck. Centro de Electrónica Industrial (CEI) | Universidad Politécnica de Madrid | cei@upm. es | www. cei. upm. es