How a buck converter actually works
A buck converter does not continuously “reduce” voltage. It repeatedly stores and releases energy, then lets the output filter turn that switching process into something that looks like DC.
Ideal steady-state CCM model. ON and OFF freeze a switching phase; VOUT remains the predicted cycle average. Animation is slowed for illustration.
First, the input feeds the inductor.
When the switch closes, the source is connected to the inductor. The inductor does not let its current change instantly, so its current ramps upward instead.
Then the inductor keeps the current moving.
Opening the switch removes the input source, but inductor current cannot disappear instantly. The diode provides a path, so stored magnetic energy continues flowing into the load.
The output voltage comes from time.
The switch spends a fraction of every cycle connected to the input. For an ideal buck converter in continuous conduction:
The real converter is less polite.
MOSFET switching loss, inductor resistance, capacitor ESR, diode drop and control dynamics all pull the real circuit away from the one-line ideal equation.