Inverting Buck-Boost Converter Calculator

About the Inverting Buck-Boost Converter Calculator

The inverting buck-boost converter is a fundamental DC-DC topology that produces a negative output voltage from a positive input. Unlike the standard buck (step-down) or boost (step-up) converter, the inverting buck-boost can produce an output magnitude either greater or less than the input, making it the most versatile single-switch topology.

This converter is widely used to generate negative supply rails for op-amps, analog circuits, and audio systems. It can also be found in battery-powered devices where a negative rail is needed alongside the main positive supply.

This Inverting Buck-Boost Converter Calculator computes the duty cycle, minimum inductance for continuous conduction mode, output capacitance for a specified ripple tolerance, switch voltage stress, input and peak currents, power loss, and efficiency metrics. Preset buttons cover typical applications from 5 V logic supplies to 48 V industrial systems. A converter topology comparison table helps you choose the right approach for your design.

When This Page Helps

This calculator improves speed and consistency while reducing avoidable mistakes in practical workflows.

How to Use the Inputs

1. Enter the positive input voltage (Vin).
2. Enter the desired negative output voltage (Vout, with or without the minus sign).
3. Enter the required output current in amps.
4. Set the switching frequency in kHz.
5. Enter the estimated overall efficiency.
6. Set the acceptable output ripple as a percentage.
7. Review duty cycle, inductance, capacitance, switch stress, and power flow.

Example Calculation

Tips & Best Practices

• Confirm the input and output units before reading the converted value.
• Round only at the end if the converted value feeds into another calculation.

When To Use This Calculator

Design an inverting buck-boost converter by calculating duty cycle, inductance, output capacitance, switch stress, and power budget. Use it when you need a repeatable calculation in the physics / general category and want the setup, result, and supporting values kept together. This is especially helpful when small input changes, unit choices, or rounding decisions can change the final number.

How To Check The Result

Start by confirming that the inputs match the formula shown on the page. Then compare the main output with the worked example and any secondary values shown by the calculator. If the result will be used in another calculation, keep extra precision until the final step and record the assumptions beside the number.

Practical Notes

Treat the result as a calculation aid rather than a substitute for context. For schoolwork, include the formula and substitution steps. For planning, technical, financial, or health-related decisions, verify important numbers against primary records, current rules, or a qualified professional before acting on them.

Frequently Asked Questions

• Why is the output voltage negative?

  The topology reverses the inductor's voltage during the off-time, delivering current to the output capacitor with reversed polarity.

• What is continuous conduction mode (CCM)?

  In CCM, the inductor current never reaches zero during a switching cycle. CCM is preferred for lower ripple and predictable behavior.

• How do I choose switching frequency?

  Higher frequency allows smaller L and C but increases switching losses. Typical range: 100 kHz to 500 kHz for most applications.

• Why does the switch see Vin + |Vout|?

  During the off-time, the inductor voltage reverses and adds to the input voltage across the switch — the MOSFET must be rated accordingly.

• Can I use this for positive output?

  No — for positive output use a buck, boost, or SEPIC converter. The inverting buck-boost inherently produces negative output.

• What efficiency should I expect?

  Typical efficiency ranges from 75% to 90%, depending on component selection, operating point, and switching frequency.