Buck (step-down) · topology: how it works
With Q on, current flows from the input into the inductor and load; with Q off, the inductor keeps its current going through the diode (or a second MOSFET). Output ≈ input × duty cycle.
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🔍 How to recognise it on a board
- ✓A single inductor with a MOSFET + diode, or two MOSFETs (synchronous buck)
- ✓No transformer; input and output share ground
- ✓On motherboards, rows of square inductors (marked R22, 1R0) around the CPU, each with MOSFETs beside it
- ✓The output is always lower than the input
Where it's used
Motherboard VRMs, graphics cards, 12 V → 5 V / 3.3 V converters, car chargers
Common ICs
LM2596MP1584Anakart VRM kontrolcüleri
Go further
A real synchronous buck example: MPPT solar chargingSimulator: buck and boostLesson: motherboard VRM