Buck Boost Converter Designer

Buck-Boost Pro | ConFinal

Professional design tool for Buck-Boost (Inverting) Converters. Calculates values for the standard inverting topology where |V_out| can be higher or lower than V_in. Includes high-voltage stress analysis and RMS current checks.

Specs & Margins

Input

Operating Point

Input (V_in)

Output |V_out|

Load (I_out)

Freq (f_sw)

kHz

Derating (Safety)

Voltage Margin

Current Margin

Targets

Efficiency (η)

Target Ripple

Inductor I_sat

Cap ESR

mΩ

Design Analysis

CCM Mode

Required Inductance (L)

— µH

—Peak I_pk

—Duty Cycle

—Power Loss

Component Sizing Guide

Buck-Boost stresses are V_in + V_out

Switch V_max — V

Diode V_R — V

In Cap I_RMS — A

Switch I_pk — A

Diode I_pk — A

Out Cap I_RMS — A

—Min C_out

—Total Ripple

—RHP Zero

Inductor Current (I_L)

Physics Explained

Dual Pulsed Current

In Buck-Boost, both Input and Output capacitors see pulsed currents. Both capacitors must be rated for high RMS current (and low ESR).

Voltage Stress

The switch and diode must withstand V_in + V_out. This is significantly higher than in Buck or Boost topologies.

RHP Zero

Like the Boost, the Buck-Boost has a Right-Half-Plane Zero that limits bandwidth. Control must be slow (f_c << f_RHPZ) to remain stable.

How to Use

Set Voltages

Define V_in and the absolute value of V_out. The topology is inverting, but input positive values for calculation.

Check Voltage Stress

Ensure your MOSFET and Diode are rated for at least V_in + V_out plus safety margin.

Capacitor Selection

Buck-Boost requires robust capacitors on both sides. Check the RMS current ratings in the Sizing Guide.