An inverting buck-boost converter turns a positive supply into a negative one that can be larger or smaller in magnitude – useful for op-amp rails, LCD bias and audio circuits.
How to use the Inverting Buck-Boost Converter Calculator
- Input voltage V_in
- Output voltage magnitude |V_out|
- Switching frequency f_sw
- Inductor ripple current ΔI_L
- Efficiency (%)
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the input voltage, the magnitude of the negative output voltage, the switching frequency, the ripple current and the efficiency.
Inputs explained
| Field | What to enter |
|---|---|
| Input voltage V_in | Units: V, mV, kV, µV, MV |
| Output voltage magnitude |V_out| | Units: V, mV, kV, µV, MV |
| Switching frequency f_sw | Units: kHz, MHz, Hz |
| Inductor ripple current ΔI_L | Units: A, mA, µA, kA |
| Efficiency (%) | A number |
What each result means
- Duty cycle D = [Output voltage magnitude |V_out|]÷([Output voltage magnitude |V_out|] + [Input voltage V_in]×[Efficiency (%)]÷100)×100
- Inductance L = [Input voltage V_in]×[Output voltage magnitude |V_out|]÷([Output voltage magnitude |V_out|] + [Input voltage V_in]×[Efficiency (%)]÷100)÷([Switching frequency f_sw]×[Inductor ripple current ΔI_L])
Example values
How the main result changes when Input voltage V_in changes and everything else stays at the example values above:
| Input voltage V_in (V) | Duty cycle D (%) |
|---|---|
| 6 | 48.0769 |
| 9 | 38.1679 |
| 12 | 31.6456 |
| 15 | 27.027 |
| 18 | 23.5849 |
| 24 | 18.797 |
Formula
D = |V_out| / (|V_out| + V_in·η), L = V_in·D / (f_sw·ΔI_L)
Worked example
Inputs — Input voltage V_in: 12 V; Output voltage magnitude |V_out|: 5 V; Switching frequency f_sw: 500 kHz; Inductor ripple current ΔI_L: 0.5 A; Efficiency (%): 90.
Results — Duty cycle D = 31.6456 %; Inductance L = 15.18987 µH.
Key terms
- Buck-boost
- A converter that can step up or down.
Frequently asked questions
Why is the output negative?
The inductor current flows through the diode in the reverse direction.
Can the output be larger than the input?
Yes – when D > 50%.
Where is it used?
Negative supply rails for analogue and display circuits.
What is the inductor peak current?
Higher than in buck or boost designs – check ratings.