LTspicePowerSim

Four-switch buck-boost — analog Type III loop

LTspicePowerSim's 3.5 V to 3.3 V buck-boost, its compensator, PWM and dead time drawn from native control parts.

Press Run: the example simulates in your browser. Open and simulate takes it to the full app, where you can change it.

Try this

Lower the input to 2.5 V and watch the boost leg take over while the output stays at 3.3 V. Then press Run again.