# Inverting Buck-Boost Converter Calculator

URL: https://speedycalculator.com/calculators/physics/inverting-buck-boost-converter/
Last updated: 2026-10-30

> The inverting buck-boost converter calculator finds the duty cycle and inductance of a converter that produces a negative output voltage of any magnitude from a positive input.

## Inputs

- Input voltage V_in (V, mV, kV, µV, MV)
- Output voltage magnitude |V_out| (V, mV, kV, µV, MV)
- Switching frequency f_sw (kHz, MHz, Hz)
- Inductor ripple current ΔI_L (A, mA, µA, kA)
- Efficiency (%)

## Results

- Duty cycle D
- Inductance L

## Formula

```
D = |V_out| / (|V_out| + V_in·η),  L = V_in·D / (f_sw·ΔI_L)
```

## Explanation

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

FieldWhat to enterInput voltage V_inUnits: V, mV, kV, µV, MVOutput voltage magnitude |V_out|Units: V, mV, kV, µV, MVSwitching frequency f_swUnits: kHz, MHz, HzInductor ripple current ΔI_LUnits: A, mA, µA, kAEfficiency (%)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 (%)648.0769938.16791231.64561527.0271823.58492418.797

## 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.

## FAQ

**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.


## Sources

- [Texas Instruments – Power supply design application notes](https://www.ti.com/power-management/overview.html)
- [OpenStax – University Physics Volume 2](https://openstax.org/details/books/university-physics-volume-2)