Hysteretic Control Embedded Boost Converter Operating at 25-MHz Switching

Abstract

A newly designed hysteretic control is proposed for a 25-MHz switching boost converter. The control part comprises the following three components: the serial connection of a resistor ( ${R} _{\mathrm {r}}$ ) and a capacitor to generate ripple signal, a comparator to adjust the output voltage ( ${V} _{\mathrm{out}}$ ), and an additional resistor ( ${R} _{\mathrm{com}}$ ) inserted between the output and the inverting input of the comparator. In order to avoid signal delays and to allow boost converter topology, the appropriate relationship between ${R} _{\mathrm{r}}$ and ${R} _{\mathrm{com}}$ is presented. The GaN transistor used has an input capacitance of 43 pF and a feedback capacitance of 11 pF at zero drain–source voltage. Owing to these low parasitic capacitances, the comparator can drive the transistor, and this multi-functional comparator configuration also reduces control signal delays. These effects enable the boost converter to operate at a switching frequency of 25 MHz, allowing ${V} _{\mathrm{out}}$ to conform to the envelope of a long term evolution signal with a 4-MHz bandwidth. This capability is quantitatively verified by means of a 3.9% normalized mean square error.