Inverting Buck-Boost Converter Calculator
Free calculate duty cycle, output voltage, or input voltage for inverting buck-boost converters with opposite polarity output.
Input Parameters
Negative value (opposite polarity)
Results
Enter values to calculate
What is an Inverting Buck-Boost Converter?
An inverting buck-boost converter is a DC-DC converter that produces an output voltage with opposite polarity to the input voltage. It can step up or step down the voltage magnitude while inverting the polarity.
Unlike standard buck-boost converters, the inverting version always produces negative output relative to the input. The duty cycle determines whether the output magnitude is larger or smaller than the input.
These converters are used in applications requiring negative voltages (op-amps, LCD displays, certain sensors) or when you need both voltage conversion and polarity inversion in a single stage.
Inverting Buck-Boost Converter Formulas
Duty Cycle
Output Voltage
How to Calculate
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1
Identify what to solve for
Determine whether you need duty cycle, output voltage, or input voltage.
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2
Use absolute values for output voltage
Since output is negative, use |V_out| (absolute value) in calculations.
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3
Apply the appropriate formula
D = |V_out|/(|V_out|+V_in), |V_out| = V_in×D/(1-D), or V_in = |V_out|×(1-D)/D.
Practical Examples
Example 1: Calculate Duty Cycle
Input is 12 V, desired output is -5 V. Calculate duty cycle.
Solution:
D = |V_out| / (|V_out| + V_in) = 5 / (5 + 12)
D = 5/17 = 0.294 (29.4%)
Example 2: Calculate Output Voltage
Input is 12 V, duty cycle is 0.5. What is the output voltage?
Solution:
|V_out| = V_in × D / (1-D) = 12 × 0.5 / 0.5
V_out = -12 V (same magnitude as input!)
Applications
Op-Amp Circuits
Generating negative supply voltages for operational amplifiers that require dual power supplies.
LCD Displays
Providing negative bias voltages required for liquid crystal displays in portable devices.
Sensors
Powering sensors and transducers that require negative voltage rails for proper operation.
Power Supplies
Creating dual-rail power supplies from single positive sources in compact electronic designs.
Frequently Asked Questions
Why is the output always negative?
The circuit topology (inductor, switch, diode arrangement) inherently inverts the polarity. The output is always opposite to the input polarity.
Can it step up and step down voltage?
Yes! When D > 0.5, |V_out| > V_in (step up). When D < 0.5, |V_out| < V_in (step down). At D = 0.5, magnitudes are equal.
What is the duty cycle range?
Duty cycle ranges from 0 to 1 (0% to 100%). However, practical limits are typically 0.1 to 0.9 to avoid extreme conditions and ensure proper operation.
How does efficiency affect the calculation?
The formulas assume 100% efficiency. For real converters, account for losses: |V_out| = η × V_in × D/(1-D), where η is efficiency (typically 0.85-0.95).
What is continuous vs discontinuous conduction mode?
CCM (continuous) means inductor current never reaches zero. DCM (discontinuous) means current reaches zero. These formulas assume CCM. DCM requires different calculations.