Ćuk Converter Calculator
Design a Ćuk buck-boost converter with inverted output. Solves duty cycle, inductors L1 and L2, and coupling capacitor for specified input/output.
How to Use
- Enter V_in, V_out magnitude (will be negative), I_out, and f_sw.
- Tool computes duty cycle, two inductors, and coupling cap C1.
Show Work
Formulas
History of the Cuk Converter
Slobodan Cuk invented the converter bearing his name at Caltech in 1977 (US Patent 4,184,197). It solved a specific problem - inverting buck-boost with low input AND output ripple - that earlier topologies could not achieve simultaneously. Cuk went on to found TESLAco and publish extensively on switched-mode converter topologies; his Caltech courses trained a generation of power electronics engineers. The topology is niche today (low-noise instrumentation supplies, specialty aerospace) but remains a classic teaching example of coupled-inductor design.
About This Calculator
Enter V_in, V_out magnitude (output is negative), load current, and f_sw. The tool computes duty D = V_out/(V_in+V_out), two inductors sized for 30-40% ripple, coupling cap C1 for 1% voltage ripple, and MOSFET voltage rating.
Slobodan Ćuk invented this topology at Caltech in 1977 (patent 4,184,197). Modern Ćuk controllers are rare vs SEPIC, but the math is the same; you can drive a Ćuk with any inverting-topology buck-boost controller with minor component swaps. Everything runs client-side.
Frequently Asked Questions
Ćuk vs SEPIC?
Ćuk: inverting output (V_out is negative relative to ground). SEPIC: non-inverting. Both are buck-boost. Ćuk has low input and output ripple (both inductors smooth) — ideal for noise-sensitive loads.
Low ripple?
Both input and output currents are continuous (L1 on input, L2 on output). Very low input EMI and output ripple compared to buck or boost alone. Used in satellite and medical supplies where noise must be minimized.
Inverted output?
V_out is negative relative to common ground. Need to flip reference or use Ćuk in a floating-output configuration. Common in op-amp dual-supply generation from single battery.
Common Use Cases
Dual-Supply Op-Amp
+12 V input → -12 V output to create ±12 V supplies from single battery.
Low-Noise Instrumentation
Analog instrument DC supply with very low ripple for precision measurement front-ends.
Satellite Power
Inverted rail for satellite electronics where EMI containment is critical.
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