Calculator KB-15
Boost converter calculator
When you need a voltage higher than the input from a battery or USB.
Result
In brief: Calculate a DC-DC boost converter: inductance, output capacitance, duty cycle, input and peak current, with an inductor current graph. Example: Inductance: 66 µH.
Calculation example
| Input voltage | 12 V |
|---|---|
| Output voltage | 24 V |
| Load current | 1 A |
| Frequency | 150 kHz |
| Current ripple | 30 % |
| Output ripple | 100 mV |
| Expected efficiency | 90 % |
| Inductance | 66 µH |
|---|---|
| Duty cycle | 55 % |
| Input current | 2.222 A |
| Inductor current ripple | 666.7 mA |
| Switch peak current | 2.556 A |
| Minimum output capacitance | 36.67 µF |
| Losses | 2.67 W |
How it is calculated
Iin = Uo · Io / (Ui · η)
L = Ui · D / (f · ΔI)
C = Io · D / (f · ΔU)
While the switch is on, the inductor stores energy from the input, and only the capacitor supplies the load. So the input current is significantly higher than the output current, and the capacitor works harder than in a buck converter.
What to look for
- Use the minimum input voltage for the calculation: that’s when the current and duty cycle are highest.
- A boost converter does not disconnect the load: when the switch is off, the input is connected to the output through the diode, and nothing limits a short circuit.
Frequently asked questions
How much current does a boost converter draw from its source?
Iin = Uout · Iout / (Uin · η). For 12→24 V, 1 A, and 90% efficiency, that’s 2.22 A: the input current is roughly as many times higher as the voltage is stepped up.
How do you calculate the inductor for a boost converter?
L = Uin · D / (f · ΔI), where D = 1 − Uin · η / Uout. For 12→24 V, 150 kHz, and ripple equal to 30% of the input current, the result is about 66 µH.
Is a boost converter module protected against short circuits?
A simple circuit isn’t protected: the input is connected to the output through the inductor and diode, and in a short circuit the current is limited only by the source. Install a fuse on the input.
