Switching Regulator Efficiency Calculator Formula
Understand the math behind the switching regulator efficiency calculator. Each variable explained with a worked example.
Formulas Used
Input Power
input_power_w = v_out * load_current_a / eff_fractionInput Current
input_current_a = v_out * load_current_a / (eff_fraction * v_in)Power Lost
power_lost_w = v_out * load_current_a / eff_fraction - v_out * load_current_aVariables
| Variable | Description | Default |
|---|---|---|
v_in | Input Voltage(V) | 12 |
v_out | Output Voltage(V) | 3.3 |
load_current_a | Output Current(A) | 2 |
efficiency_pct | Efficiency(%) | 90 |
eff_fraction | Derived value= efficiency_pct / 100 | calculated |
How It Works
Switching Regulator Efficiency
Formulas
P_in = P_out / Efficiency
I_in = P_out / (Efficiency x V_in)
Switching regulators convert voltage using rapid switching and an inductor. They achieve 85-95% efficiency regardless of voltage ratio, far better than linear regulators for large step-downs.
Worked Example
12 V to 3.3 V at 2 A with 90% efficiency.
- 01P_out = 3.3 x 2 = 6.6 W
- 02P_in = 6.6 / 0.9 = 7.33 W
- 03I_in = 7.33 / 12 = 0.611 A
- 04Power lost = 7.33 - 6.6 = 0.73 W
Frequently Asked Questions
Buck vs boost vs buck-boost?
Buck steps voltage down, boost steps up, buck-boost can do either. Choose based on your input vs output voltage relationship.
What affects efficiency?
Switching frequency, inductor DCR, MOSFET Rds(on), diode losses, and controller quiescent current all reduce efficiency.
Why not always use switching regulators?
They generate switching noise (EMI). Linear regulators are preferred for noise-sensitive circuits like ADCs and audio.
Ready to run the numbers?
Open Switching Regulator Efficiency Calculator