Boost Converter Calculator (Duty Cycle and Inductor)
Duty cycle, inductor value, ripple and peak current, and input current of a step-up (boost) converter from the voltages, load current, switching frequency and efficiency.
Results
The dashed line marks the value you entered.
What this tool does
In a boost converter the inductor charges while the switch is on and dumps into the output when it opens, so the ideal duty cycle is 1 − Vin ÷ Vout. Power in equals power out plus losses, which means the input current is larger than the output current by at least the voltage ratio — a 5 V to 12 V boost drawing 1 A at the output pulls about 2.7 A from the source at 90 % efficiency. The inductor carries that input current, so size it and its saturation rating for the input side, with ripple often chosen at 20–40 % of it; very high boost ratios get inefficient.
Formula
D = 1 − Vin × η ÷ Vout (ideal: 1 − Vin ÷ Vout) · L = Vin × D ÷ (f × ΔI) · Iin = Vout × Iout ÷ (Vin × η)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
vi | Input voltage | V |
vo | Output voltage | V |
io | Output current | A |
f | Switching frequency | kHz |
rp | Inductor current ripple (share of the average inductor current) | % |
et | Efficiency | % |
L | Inductance needed | µH |
D | Duty cycle, allowing for losses | % |
DI | Duty cycle, lossless | % |
II | Average input current | A |
DL | Ripple current, peak to peak | A |
IP | Peak inductor current | A |
ST | Can this converter do it? | — |
Worked example
- Input voltage5 V
- Output voltage12 V
- Output current1 A
- Switching frequency100 kHz
- Inductor current ripple (share of the average inductor current)30 %
- Efficiency90 %
- Inductance needed39.1 µH
- Duty cycle, allowing for losses62.5 %
- Duty cycle, lossless58.3 %
- Average input current2.67 A
- Ripple current, peak to peak0.80 A
- Peak inductor current3.07 A
- Can this converter do it?Yes
Limitations
- Electrical installations are governed by national wiring rules. Cable sizing also depends on installation method, grouping, ambient temperature and protection devices, which this calculator does not evaluate.
- Coverage and consumption figures vary between products. Take the values from the manufacturer's datasheet for the product you are actually using.