Inverting Buck Boost Converter Calculator

Inverting Buck-Boost Converter Voltage

An inverting buck-boost converter steps a DC input voltage up or down while reversing polarity. Unlike a standard buck or boost converter, the output is negative relative to ground. This topology is common in battery-powered systems that need a negative rail.

Formula

$$V_{out} = -V_{in} \times \frac{D}{1 - D}$$

$V_{in}$ is the input voltage, $D$ is the duty cycle (0 to 1), and the negative sign indicates inverted polarity. Rearranging to solve for duty cycle:

$$D = \frac{|V_{out}|}{V_{in} + |V_{out}|}$$

Design Notes

Duty cycle must stay between 0% and 100% (exclusive) for valid operation. At D = 50%, the output magnitude equals the input. Higher duty cycles produce larger inverted outputs. Component selection, switching frequency, and inductor current ripple affect real-world efficiency and regulation.

Frequently Asked Questions

Why is the output voltage negative?

The inverting buck-boost topology connects the output with reversed polarity relative to the input. The negative sign in the formula reflects this inversion.

What duty cycle gives Vout equal to -Vin?

At D = 50%, Vout = -Vin. The converter inverts the input magnitude when the duty cycle is exactly half.

Can duty cycle exceed 50%?

Yes. Duty cycles above 50% produce output magnitudes larger than the input. Values must remain below 100% for continuous conduction.

How is this different from a regular buck-boost?

A standard buck-boost also inverts polarity. The inverting buck-boost uses a similar energy-transfer principle but with a different switch and diode arrangement optimized for negative outputs.

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Inverting Buck Boost Converter Calculator

Inverting Buck-Boost Converter Voltage

Formula

Design Notes

Frequently Asked Questions

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