Buck-Boost Converter Calculator

A buck-boost converter is a DC power supply circuit that can both step voltage down (like a buck) and step it up (like a boost), while also inverting the polarity — useful when your output voltage needs to be negative or differ significantly from the input. Enter your Input Voltage, Output Voltage, Output Current, Switching Frequency, Current Ripple Factor, and Efficiency into the Buck-Boost Converter Calculator to find the required Duty Cycle. Secondary outputs include Inductor Value, Average Input Current, Peak Inductor Current, Current Ripple, and Input Power.

V

DC input voltage to the converter

V

Desired output voltage (negative for inverting)

A

Maximum output current required

Hz

PWM switching frequency

Inductor current ripple as fraction of average current

%

Estimated converter efficiency

Results

Duty Cycle

--

Inductor Value

--

Average Input Current

--

Peak Inductor Current

--

Current Ripple

--

Input Power

--

More Electrical & Electronics Tools

Frequently Asked Questions

What is a buck-boost converter?

A buck-boost converter is a DC-to-DC switching converter that can either step up (boost) or step down (buck) the input voltage. In inverting topology, it produces a negative output voltage with respect to ground.

How do I calculate the duty cycle for a buck-boost converter?

The duty cycle for an inverting buck-boost converter is calculated as D = |Vout| / (Vin + |Vout|), where Vout is the desired output voltage and Vin is the input voltage.

What inductor value should I use?

The inductor value depends on the switching frequency, current ripple requirements, and operating conditions. Higher switching frequencies allow smaller inductors, while lower current ripple requires larger inductors.

Why does a buck-boost converter produce negative voltage?

The inverting buck-boost topology inherently produces a negative output voltage because of how the inductor and switch are connected. The output is referenced to the negative terminal of the input.

What affects the efficiency of a buck-boost converter?

Efficiency depends on switching losses, conduction losses in the MOSFET and diode, inductor resistance, and operating duty cycle. Buck-boost converters typically have lower efficiency than buck or boost converters alone.

How do I choose the switching frequency?

Higher switching frequencies allow smaller passive components but increase switching losses. Common frequencies range from 50kHz to 500kHz, with 100-200kHz being typical for many applications.

What is current ripple and why does it matter?

Current ripple is the variation in inductor current during switching cycles. Lower ripple reduces output voltage ripple and stress on components but requires larger inductors.