Switching Regulator (Buck) Component Calculator

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Electrical & Electronics Engineering — Circuits, Power Systems, Electronics Lab

Tranche

tranche-5

Evidence ID

t5-006

Ledger rows

1

No ledger note is attached.

Review findings

NEEDS_REVIEW because the exact capacitor formula and the definitions of current and voltage ripple are missing. The four capacitor outputs are conditional results using the ideal CCM triangular-ripple formula Cout=ΔIL/(8·f·ΔVout); they must not be presented as unqualified design values. The existing honest-label warning is appropriate but should explicitly mention the capacitor ripple model, CCM validity, ESR, ripple-current rating, and input constraints.

Formula and scope findings

• D=Vout/Vin is the ideal continuous-conduction, lossless buck duty-cycle formula; it requires Vin>0 and normally 0<Vout<Vin. It omits switch, diode, inductor, and conduction losses.
• L=(Vin−Vout)·D/(f·ΔIL) is correct for ideal CCM operation when f is switching frequency in hertz and ΔIL is the peak-to-peak inductor-ripple current in amperes.
• The capacitance formula is not specified. “Cout from ΔVout ripple spec” is ambiguous: an ideal-capacitor triangular-ripple estimate is Cout=ΔIL/(8·f·ΔVout), but ESR ripple, ripple-current rating, control-loop constraints, and the definition of ΔVout must also be addressed.
• Peak inductor current is listed as an output but no formula is supplied. Under average-current CCM with triangular ripple, Ipk=Iout+ΔIL/2.
• The specification does not define whether ripple percentages are relative to Iout and Vout, nor whether ripple values are peak-to-peak, peak, or RMS.

Unit assumptions

• Vin and Vout are in volts, Iout and ΔIL are in amperes, switching frequency f is in hertz, L is returned in henries, and Cout is returned in farads.
• The test vectors interpret current-ripple target as peak-to-peak ΔIL=(ripple_current_percent/100)·Iout.
• The test vectors interpret output-voltage-ripple target as peak-to-peak ΔVout=(ripple_voltage_percent/100)·Vout.
• For conditional Cout values, the assumed formula is Cout=ΔIL/(8·f·ΔVout), representing ideal capacitor-only ripple from triangular inductor current.
• The test vectors assume ideal lossless CCM operation and triangular inductor current ripple.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

The calculator specification exposes invalid or ambiguous behavior at Vin=0, produces a nonphysical zero inductance at Vout=Vin, and can produce a negative inductance when Vout exceeds Vin. Ripple-percentage convention is also unspecified and changes the component values.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "Vin_V": 24,
    "Vout_V": 12,
    "Iout_A": 2,
    "switching_frequency_Hz": 500000,
    "current_ripple_percent_of_Iout": 30,
    "voltage_ripple_percent_of_Vout": 1
  },
  "expected_outputs": {
    "duty_cycle": 0.5,
    "inductor_ripple_A_pp": 0.6,
    "inductor_uH": 20,
    "output_capacitor_uF": 1.25,
    "peak_inductor_current_A": 2.3
  },
  "working": "ΔIL=(30/100)·2=0.6 A. D=12/24=0.5. L=(24−12)·0.5/(500000·0.6)=6/300000=0.000020 H=20 µH. ΔVout=(1/100)·12=0.12 V. Cout=0.6/(8·500000·0.12)=0.6/480000=0.00000125 F=1.25 µF. Ipk=2+0.6/2=2.3 A."
}

Related workflows

No source-defined multi-instrument workflow membership is recorded.

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json · VERIFIED_CLEAN
• evidence-tranche5/tranche5-results.json
• BOUNDARY_HAZARD_CATALOG.json