Enhancements of the Multiple Input Buck Converter for Envelope Tracking Applications

1. 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 4th order Bessel filter is presented here. A multiphase MIBuck is also proposed. Experimental results are shown. Why4th order Bessel? DesignHints: Mission of the output filter in ET: • Reject the switching frequency . Keep waveform. • Guarantee CCM Grupo de Sistemas Electrónica de Alimentación • Besselfilter has flat pass-band and flat group-delay. • Filter adapted to the Switching Network Impedance • Switching frequency rejection (40 dB) • Angular switchingfrequencyfor 40 dB Rejection • Boundary angular switchingfrequencyfor MCC 4th ORDER MIBuck • fs = 4 MHz fcutt-off= 1 MHz 4th ORDER MultiphaseMIBuck • 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 theMultiphaseMIBuck.