Buck-Boost Converter Efficiency Maximization via a Nonlinear Digital Control Mapping for Adaptive Effective Switching Frequency

A nonlinear control loop mapping has previously been designed for mitigating the dead zone of a noninverting buck-boost converter while minimizing state variable perturbation. This paper derives a new nonlinearity that enables a converter with fixed switching frequency to achieve reduced switching loss as though operating at an effective switching frequency lower than the actual. The new control loop nonlinearity accomplishes this by interleaving a specified fraction of pass-through and nonpass-through switching periods. The derived nonlinearity also reduces the increase in waveform ripple associated with a switching frequency reduction. Through adapting the effective switching frequency across the full range of conversion ratios and loads, reductions in loss up to 58% are realized.