Start with the power stage
Choose the topology, enter its electrical targets, then use the preset only as a known starting point. Check current ripple and device stress before believing any loss number.
This guide explains what each calculator input means, how the first-pass equations are formed, and where a real converter can depart from the ideal model. Examples follow Formula → Substitute → Answer so the numbers can be checked by hand.
Source standard. Design claims are linked to official manufacturer application notes and original IEEE papers. All figures below are original explanatory diagrams—not copied publication figures. Equations are screening models; validate final hardware with device curves, simulation, thermal analysis, double-pulse testing, and safe laboratory measurements.
Choose the topology, enter its electrical targets, then use the preset only as a known starting point. Check current ripple and device stress before believing any loss number.
Measured Eon/Eoff at comparable voltage, current, gate resistance, and temperature is preferable. Rise/fall-time estimates are useful when energy data is unavailable, but they are sensitive to parasitics and gate-drive conditions.
RDS(on) rises with junction temperature, which raises conduction loss again. Iterate loss → temperature → resistance until the result settles.
A warning is not a component approval. Check absolute maximum ratings, repetitive transient capability, SOA, magnetics saturation, capacitor ripple rating, creepage, clearance, and protection response.
The calculator exposes only the fields relevant to the selected topology. This map groups the quantities used across all modes.
| Symbol / input | Meaning | Unit | Why it matters |
|---|---|---|---|
| VIN, VOUT | DC input and regulated output voltage | V | Set conversion ratio and voltage stress. |
| VAC,rms, fline | AC-line RMS voltage and line frequency | V, Hz | PFC only: line peak, current, and twice-line ripple. |
| IOUT, POUT | Load current and delivered power | A, W | Determine average device and magnetic current. |
| η, PF | Assumed efficiency and input power factor | ratio | Translate output power to realistic input current. |
| D, ton, fs | Duty ratio, on-time, switching frequency | ratio, s, Hz | Set conduction share, energy per cycle, ripple, and switching events. |
| L, ΔIL | Inductance and peak-to-peak current ripple | H, A | Set CCM/DCM boundary, peak current, RMS current, and saturation risk. |
| C, ESR, Iripple | Capacitance, series resistance, capacitor ripple current | F, Ω, A | Set output ripple, heating, and lifetime stress. |
| RDS(on),25, αR | MOSFET on-resistance at 25 °C and temperature coefficient | Ω, 1/°C | Drive conduction loss and thermal feedback. |
| tr, tf | Drain-voltage/current overlap transition times | s | Enable a simple hard-switching overlap estimate. |
| Eon, Eoff | Measured switching energies for one event | J | Preferred switching-loss input when test conditions match. |
| Qg, Qgd, VGP | Total gate charge, Miller charge, plateau voltage | C, C, V | Set driver power and estimated transition time. |
| Rg,int/ext, Isource/sink | Gate resistance or driver current capability | Ω, A | Control switching speed, ringing, overshoot, and false turn-on margin. |
| Coss, Eoss | Output capacitance or stored output energy | F, J | Contribute to node-transition energy; strongly voltage-dependent. |
| Qrr | Body-diode/recovery charge | C | Adds commutation energy and peak current. |
| td, VF | Dead time and conducting-diode forward drop | s, V | Too short risks shoot-through; too long raises diode loss. |
| TA, TC, Rθ | Ambient/case temperature and thermal resistance | °C, °C/W | Convert device loss to estimated junction temperature. |
| Lr, Cr, Lm | Series resonant L/C and transformer magnetizing inductance | H, F, H | Set LLC/CLLC resonances, gain, circulating current, and ZVS range. |
| n, Ln, Qe | Turns ratio, Lm/Lr, normalized load quality factor | ratio | Shape the resonant gain curve and load dependence. |
| Vmargin, Imargin | Design headroom above predicted stress | % | Allows for tolerance, transient, ringing, and measurement uncertainty. |
Datasheet conditions matter: a quoted 5 mΩ at 10 V gate drive and 25 °C is not automatically valid at 6 V gate drive and 125 °C. Use curves or a conservative measured value at the actual operating point.
RMS—not average current—sets resistive heating. The second expression is for a triangular ripple centered on the average.
The linear coefficient is a convenience. A normalized on-resistance curve from the selected device is better.
Use one method—not both for the same overlap energy. Energy curves or double-pulse measurements capture more real behavior than the linear overlap model.
Prefer Eoss/Qoss curves because Coss is nonlinear. Avoid counting the same energy twice if the switching-energy data already includes it.
The factor of two assumes two dead-time intervals per complete switching period. Confirm the actual commutation sequence.
Do not mix case-referenced and ambient-referenced paths. PCB copper, airflow, interface materials, and neighboring heat sources change the effective resistance.
Manufacturer derivations and loss categories: TI, synchronous-buck efficiency calculation, TI, power loss with common-source inductance, and TI, boost-converter design example. Research extensions include MOSFET switching-loss modeling (IEEE), datasheet-driven SiC switching prediction (IEEE), and temperature-dependent SiC reverse-recovery modeling (IEEE).
CCM/DCM boundary: the ideal triangular inductor current reaches zero when IOUT = ΔIL,pp/2. Below that load the converter enters DCM and the simple duty relationship changes.
See TI’s synchronous-buck efficiency method, TI’s dead-time analysis, and IEEE analysis of common-source inductance and Kelvin source connection.
Design and loss context: TI AN-1696 boost design example and IEEE datasheet-based MOSFET/diode half-bridge loss model.
Dead-time and Miller-coupling guidance: TI, configurable dead time and dV/dt turn-on and Infineon, parasitic-induced false turn-on.
See TI’s detailed common-source-inductance loss analysis, Infineon’s VGS ringing/layout guidance, and the corresponding IEEE device-switching study.
For a real transformer current waveform, calculate RMS over each device’s actual conduction interval.
For transformer loss and insulation context, see IEEE Transactions on Power Electronics: high-frequency transformer design with medium-voltage insulation.
Definitions for Re, n, and gain depend on whether the primary is half bridge or full bridge and on the rectifier/load reflection convention. Keep one convention throughout the design.
Primary sources: TI LLC design procedure for UCC29950, TI explanation of LLC gain, Q, and Ln, and A Complete Step-by-Step Optimal Design for LLC Resonant Converter (IEEE).
Prime marks denote quantities referred to the chosen side. Confirm how your turns ratio n is defined before applying n².
ZVS energy screen:
This necessary-energy check does not prove ZVS; nonlinear Coss, dead time, magnetizing current, device capacitance, and the exact commutation path must be included.
Primary sources: TI’s bidirectional CLLLC topology application brief and Design Methodology of Bidirectional CLLC Resonant Converter (IEEE). For bidirectional transitions, see automatic forward/backward LLC transition (IEEE).
Mode selection: CCM has lower peak current but hard-switching/recovery challenges. Critical/boundary conduction turns on near zero inductor current but varies frequency. DCM has an interval of zero current and higher peaks. The controller, EMI filter, magnetics, sensing, and loss model must match the selected mode.
Topology research: Totem-Pole Boost Bridgeless PFC at the Boundary of DCM/CCM (IEEE). General switching and recovery context: TI power-device switching-loss overview.
The capacitive component follows charge balance; the ESR component changes immediately with capacitor current.
Use the ripple-current spectrum and frequency/temperature-dependent impedance, not only a DC ESR number.
Skin and proximity effects raise winding resistance at switching frequency and harmonics.
Use manufacturer loss curves or a waveform-aware model for the actual core material. A single generic Steinmetz fit may be inaccurate for nonsinusoidal excitation.
Capacitor application caution: Murata’s polymer-capacitor design guidance. Magnetic modeling research: IEEE core-loss calculation method for DC/DC power converters.
Failure and protection references: TI short-circuit and shoot-through protection brief, TI dead-time optimization, and IEEE Open Journal thermal-management validation for high-power SiC MOSFETs.
Links point to the original publisher or manufacturer. Access to some IEEE full texts may depend on the reader’s institution; the abstract and bibliographic record remain useful for traceability.
Each item below is identified by IEEE Xplore as a Journals & Magazine publication; conference-only papers are not used as the principal journal references in this guide.
This guide is educational and intended for early design screening. It does not certify component suitability, product safety, EMC, insulation, reliability, or regulatory compliance. Mains and high-energy converters can cause fire, electric shock, arc flash, and equipment damage. Use qualified supervision, appropriate probes and PPE, current-limited sources, isolation where required, and a formal design review.
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