Buck-Boost Converter CCM Ripple & Inductance Calculator

The inverting Buck-Boost topology stores energy in the inductor during switch ON time and dumps energy into the load during switch OFF time.

Continuous Conduction Mode (CCM) ensures inductor current never drops to zero during the switching cycle.

Duty cycle D governs the conversion ratio: D < 0.5 steps down (buck), while D > 0.5 steps up (boost).

Inductor ripple current is determined by input voltage, ON-time, and inductance value.

Output capacitor sustains total load current during the switch ON phase, creating voltage ripple Delta_Vout.

Duty cycle shows PWM gating requirements for closed-loop control.

Inductor ripple current should typically be sized between 20% and 40% of average inductor current.

Critical inductance confirms whether the converter will maintain CCM under light loads.

• Switching frequency: Higher frequencies dramatically reduce required L and C sizes at the expense of switching losses.
• Duty cycle: As D exceeds 0.7, peak inductor and switch current stresses rise sharply.
• Capacitor ESR: Real capacitors have Equivalent Series Resistance that adds ESR * Delta_IL to voltage ripple.

• Designing battery-powered power supplies where battery voltage can drop above or below regulated rail (e.g., 4 Li-ion cells powering 15V).
• Power electronics component selection and thermal stress analysis.

• Assumes ideal lossless switches and diodes without forward drop voltages.
• Assumes pure capacitive filtering without ESR ripple contributions.