What does an inverting buck-boost converter do?

An inverting buck-boost converter is a switching power supply topology that inverts the polarity of the input voltage while simultaneously stepping it up or down in magnitude. It produces a negative output voltage from a positive input, which is useful for powering analog circuits that need both positive and negative rails.

What is the output voltage formula?

Vout = −Vin × D / (1 − D), where D is the duty cycle (0 to 1). A duty cycle of 0.5 with Vin = 5 V produces Vout = −5 V. Duty cycles above 0.5 step up the magnitude; below 0.5 step it down.

How does the Inverting Buck-Boost Converter Calculator find the duty cycle?

How do I choose the inductor and capacitor values?

Enter the switching frequency fsw, the allowable inductor current ripple ΔIL (typically 20–40 % of maximum load current), and the allowable output voltage ripple ΔVout. The Inverting Buck-Boost Converter Calculator computes L = Vin × D / (ΔIL × fsw) and C = Iout × D / (ΔVout × fsw).

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Inverting Buck-Boost Converter Calculator

How to Use Inverting Buck-Boost Converter Calculator

The Inverting Buck-Boost Converter Calculator sizes a switching power supply in four steps.

Enter Input and Output Voltages — Type the supply voltage Vin (positive) and the desired output magnitude |Vout|. The Inverting Buck-Boost Converter Calculator instantly shows the required duty cycle D.
Enter Switching Frequency and Load — Input the switching frequency fsw (kHz) and the maximum load current Iout (A).
Set Ripple Budgets — Enter the allowable inductor current ripple ΔIL and output voltage ripple ΔVout. The calculator outputs the minimum inductor value L and minimum output capacitor C.
Review the Summary — Check duty cycle, peak inductor current, and component ratings to confirm the design is within safe operating limits.

Formula & Theory — Inverting Buck-Boost Converter Calculator

The Inverting Buck-Boost Converter Calculator implements the standard continuous-conduction-mode (CCM) equations:

Vout = −Vin × D / (1 − D)
D    = |Vout| / (Vin + |Vout|)
L    = Vin × D / (ΔIL × fsw)
C    = Iout × D / (ΔVout × fsw)
IL_peak = Iout / (1 − D) + ΔIL / 2

Symbol	Meaning	Unit
Vin	Input voltage	V
Vout	Output voltage (negative)	V
D	Duty cycle	0–1
fsw	Switching frequency	Hz
ΔIL	Inductor current ripple	A
ΔVout	Output voltage ripple	V
L	Minimum inductor value	H
C	Minimum output capacitor	F
IL_peak	Peak inductor current	A

Why Inverting?

Unlike a standard buck (step-down) or boost (step-up) converter, the inverting buck-boost flips the output polarity. This makes it ideal for generating a negative rail from a single positive supply without a transformer.

Practical Design Notes

Keep D in the range 0.2–0.8 for best efficiency. Select the next standard inductor value above the calculated minimum, and choose output capacitors with low ESR to minimize ripple.

Use Cases for Inverting Buck-Boost Converter Calculator

The Inverting Buck-Boost Converter Calculator supports electronics design and education:

Analog and audio circuits — Generate the negative rail (−12 V or −5 V) needed by op-amps, audio DACs, and analog front-ends from a single positive supply.
Sensor interfaces — Drive sensors that require a negative reference or bipolar excitation voltage using a single-supply power bus.
LED driver design — Build constant-current LED drivers with polarity inversion for specific LED matrix configurations.
Battery-powered systems — Generate a stable negative output from a Li-ion or NiMH battery to power mixed-signal circuitry.
Power electronics education — Study non-isolated DC–DC converter topology, duty-cycle control, and passive component sizing with interactive formulas.
Prototype PCB design — Size L and C before schematic entry to reduce component revision cycles during hardware bring-up.