A mitigation solution for bifurcations in a low-power 4-Switch Buck-Boost converter (4SBB)

The trend in batteries will offer an ever wider voltage range between charge and discharge. The need for DC-DC noninverting Buck-Boost converters is by extent growing to supply tiny systems which need for example a regulated input voltage at 3.3 V while the battery voltage can vary from 4.2 V down to about 2 V. The power management solutions need to be efficient to extend the battery life before recharging, to successfully address line and load transients and to be cost attractive. The 4-Switch Buck-Boost converter (4SBB) appears to be an interesting solution to fulfill the aforementioned needs. A prototype has been implemented on 0.25 um ON semiconductor with external LC output filter. Bifurcations have been detected for very specific conditions. To deal with them, an extra digital control loop has been implemented on FPGA to control the hysteresis of the PWM modulator in case of bifurcations. Simulations and experimental results are provided to prove the effectiveness of the solution. Furthermore, the gain in efficiency is evaluated through simulation for several operating conditions.