Switch, rectifier and efficiency budget
Buck-leg hard-switching losses with Miller timing, reverse recovery, dead time and temperature feedback.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Assumptions
- Buck commutation leg with ideal duty VO/VIN and fixed triangular ripple. Efficiency sweep is restricted to CCM.
- Reverse-recovery loss is assigned to the high-side turn-on event once; gate loss is assigned to the driver supply. No double counting of these terms is intended.
- Thermal feedback uses linear RDS(T); equal, independent effective thermal resistances are assumed. Diode temperature, magnetic core loss and switching-node parasitics are omitted.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Rectifier
- diode
- Input voltage
- 24 V
- Output voltage
- 5 V
- Design output current
- 3 A
- Inductor ripple peak-to-peak
- 0.8 A
- Switching frequency
- 300000 Hz
- High-side RDS(on) at 25 °C
- 0.03 Ω
- Low-side RDS(on) at 25 °C
- 0.02 Ω
- RDS temperature coefficient
- 0.004 1/K
- Diode / body-diode forward voltage
- 0.6 V
- Commutated rectifier recovery charge
- 1e-8 C
- High-side total gate charge
- 2e-8 C
- Low-side gate charge
- 2e-8 C
- High-side Miller charge
- 5e-9 C
- Gate drive
- 5 V
- Miller plateau
- 3 V
- Total turn-on gate resistance
- 5 Ω
- Total turn-off gate resistance
- 5 Ω
- High-side output-capacitance energy
- 1e-7 J
- Dead time per switching edge
- 2e-8 s
- Inductor DCR
- 0.05 Ω
- Controller supply current
- 0.002 A
- Each FET thermal resistance
- 40 K/W
- Ambient temperature
- 25 °C
Results
- Design-load efficiency
- 86.5217 %
- Total modeled loss
- 2.3367 W
- High-side FET loss
- 0.381033 W
- Rectifier loss
- 1.425 W
- Inductor copper loss
- 0.452667 W
- Gate-drive supply loss
- 0.03 W
- High-side temperature
- 40.2413 °C
- Low-side temperature
- No low-side MOSFET °C