Cuk Converter Calculator

CUK Converter Examples

Example 1: High-Voltage Step-Down

Given: Input Voltage (V_s) = 325 V, Output Voltage (V_o) = 100 V, Output Power (P_out) = 500 W, Ripple = 10%, Switching Frequency (f_sw) = 50,000 Hz

Duty Cycle (D): D = |V_o| / (|V_s| + |V_o|) = 100 / (325 + 100) = 0.235 or 23.5%
Output Current (I_out): 500 / 100 = 5.00 A
Inductor Ripple (ΔI_L1): 0.1 × (500/325) = 0.154 A
Inductor Ripple (ΔI_L2): 0.1 × 5 = 0.5 A
Inductor L1: 325×0.235/(0.154×50000) = 0.00994 H = 994 µH
Inductor L2: 100×(1-0.235)/(0.5×50000) = 0.00306 H = 3059 µH
Capacitor C1: 5×0.235/(10×50000) = 2.35 µF
Capacitor C2: 0.5/(8×50000×10) = 0.00125 µF = 0.125 µF
Load Resistor: 100/5 = 20 Ω

Example 2: Step-Up (Boost) Mode

Given: Input Voltage (V_s) = 10 V, Output Voltage (V_o) = 15 V, Output Power (P_out) = 30 W, Ripple = 10%, Switching Frequency (f_sw) = 100,000 Hz

Duty Cycle (D): 15 / (10 + 15) = 0.6 or 60%
Output Current (I_out): 30 / 15 = 2.00 A
Inductor Ripple (ΔI_L1): 0.1 × (30/10) = 0.3 A
Inductor Ripple (ΔI_L2): 0.1 × 2 = 0.2 A
Inductor L1: 10×0.6/(0.3×100000) = 0.0002 H = 200 µH
Inductor L2: 15×(1-0.6)/(0.2×100000) = 0.0003 H = 300 µH
Capacitor C1: 2×0.6/(1.5×100000) = 0.000008 µF = 8 µF (assuming ΔV_C1 = 1.5V, 10% of V_o)
Capacitor C2: 0.2/(8×100000×1.5) = 0.000167 µF = 0.167 µF
Load Resistor: 15/2 = 7.5 Ω

Example 3: Moderate Step-Down

Given: Input Voltage (V_s) = 24 V, Output Voltage (V_o) = 12 V, Output Power (P_out) = 60 W, Ripple = 10%, Switching Frequency (f_sw) = 75,000 Hz

Duty Cycle (D): 12 / (24 + 12) = 0.333 or 33.3%
Output Current (I_out): 60 / 12 = 5.00 A
Inductor Ripple (ΔI_L1): 0.1 × (60/24) = 0.25 A
Inductor Ripple (ΔI_L2): 0.1 × 5 = 0.5 A
Inductor L1: 24×0.333/(0.25×75000) = 0.000426 H = 426 µH
Inductor L2: 12×(1-0.333)/(0.5×75000) = 0.000213 H = 213 µH
Capacitor C1: 5×0.333/(1.2×75000) = 0.0000185 µF = 18.5 µF (assuming ΔV_C1 = 1.2V, 10% of V_o)
Capacitor C2: 0.5/(8×75000×1.2) = 0.000069 µF = 0.069 µF
Load Resistor: 12/5 = 2.4 Ω

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CUK Converter Examples

Example 1: High-Voltage Step-Down

Example 2: Step-Up (Boost) Mode

Example 3: Moderate Step-Down