MOSFET Conduction + Switching Loss
Estimate total MOSFET power loss — I²R conduction plus turn-on/turn-off switching energy — for a hard-switched converter.
Your recent runs (stored only in your browser)
No calculations yet — results land here so you can compare runs.
The engineering
A hard-switched MOSFET burns power two ways: static conduction loss while it carries current (I²R across R_DS(on), scaled by how much of the period it is on) and dynamic switching loss during the finite overlap of voltage and current at each transition. This card sums both so you can size a heatsink or trade frequency against efficiency.
The triangular-overlap ½·V·I·t model is the classic Infineon first-order estimate — good for a bench sanity check, optimistic against reality. Real transitions add reverse-recovery of the freewheeling diode, output-capacitance (Coss) loss, and gate-drive loss, and R_DS(on) rises roughly 0.4%/°C, so evaluate it at the hot junction temperature, not the 25 °C datasheet number. If switching loss dominates conduction, drop frequency or improve gate drive before reaching for a bigger die.
Where this math comes from
The power MOSFET went commercial in the mid-1970s (International Rectifier's HEXFET, 1978) and immediately forced designers to budget loss differently than with bipolar parts: no minority-carrier storage, but a real R_DS(on) that climbs with temperature and finite switching transitions that cost energy every cycle. Application engineers at International Rectifier and later Infineon codified the two-term loss model that every converter designer now uses.
The ½·V·I·t overlap approximation became the standard back-of-envelope figure in Infineon and IR application notes through the 1990s and 2000s. It deliberately trades accuracy for a formula you can evaluate at a bench with a datasheet — the more exact treatments integrate the actual gate-charge waveform, but the triangle gets you within a factor that matters for first-cut thermal sizing.
- 1976Siliconix / International RectifierFirst commercial vertical power MOSFETs reach the market.
- 1978International RectifierHEXFET launched — R_DS(on) becomes the loss metric designers optimize.
- 1999Infineon TechnologiesSpun out of Siemens; CoolMOS superjunction parts sharpen the loss trade-offs.
- 2006Infineon application engineeringPublishes application notes standardizing the conduction + ½·V·I·t switching-loss model.
See the full timeline of the math behind every calculator →
Runs entirely in your browser — nothing you enter leaves this page. Your recent runs are stored only on your device.