Centro de Electrónica Industrial (CEI) | Universidad Politécnica de Madrid | [email protected] | www.cei.upm.es
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.
Why 4th order Bessel?
Mission of the output filter in ET:
Bessel filter has flat pass-band and flat group-delay.
Reject the switching frequency . Keep waveform.
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.
CONCLUSIONS
Enhancements of the Multiple Input Buck Converter for Envelope Tracking Applications
P. Fernández
Grupo de Sistemas Electrónica de Alimentación
Switching frequency rejection (40 dB)
Design Hints:
Guarantee CCM
Filter adapted to the Switching Network Impedance
4th ORDER MIBuck
4th ORDER Multiphase MIBuck
Multiphase operation introduces a notch at the
switching frequency, so the cutt-off frequency of the
filter can be increased with less switching noise
fs = 4 MHz fcutt-off= 1 MHz
fs = 4 MHz fcutt-off= 2 MHz
Angular switching frequency for 40 dB Rejection Boundary angular switching frequency for MCC