How this calculator works
The inverting buck-boost stores energy while its switch is on and delivers it to the opposite-polarity output while off. Enter a negative output voltage relative to the input return. Inductor ripple follows the input voltage during on-time. The ideal model assumes continuous conduction and excludes switching and conduction losses.
Formula
Vo = -Vi D/(1-D); D = |Vo|/(Vi+|Vo|); L = Vi D/(fs deltaI).
Worked example
With 12 V input and D = 0.25 the ideal output is -4 V. At 100 kHz with 0.3 A ripple, the inductance is 0.0001 H.
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Frequently asked questions
Does this include efficiency?
No. It uses an ideal power stage. Real semiconductor drops, winding resistance and switching losses alter the required duty cycle.
What does ripple current mean?
The entered ripple is the difference between maximum and minimum inductor current within one switching cycle.
Can this model discontinuous conduction?
No. If current reaches zero for part of the cycle, conversion ratio also depends on the load. Check the conduction mode and controller limits separately.