24W flyback transformer calculation: 12V / 2A
This example runs a built-in preset through the existing app calculation engine. Inputs, electrical results and one core-and-winding candidate are shown for review and reproduction.
What does this example verify?
This is a software calculation example with selected basic formulas and loss totals cross-checked. No prototype measurements are included, so it does not establish a percentage accuracy against hardware.
Inputs and constraints
| Item | Value or condition |
|---|---|
| Built-in preset | adapter_24w |
| DC bus (minimum / nominal / maximum) | 90 / 310 / 375 V DC |
| Output / rectifier drop | 12 V / 2 A / 0.7 V |
| Mode / frequency | DCM / 65 kHz |
| Maximum duty / k factor | 0.45 / 0.5 |
| Assumed efficiency (input) | 83% |
| Ambient / rise limit / cooling | 40°C / 40°C / natural cooling |
| Winding and optimization settings | Thermal class F, heavy insulation, non-interleaved, balanced, K_u = 0.4 |
Electrical specification results
| Item | Value or condition |
|---|---|
| Output / input power from efficiency assumption | 24 / 28.916 W |
| Target magnetizing inductance | 248.372 μH |
| Target primary-to-secondary turns ratio Np/Ns | 5.798 |
| Specification-stage primary peak current | 1.893 A |
Core and winding candidate
| Item | Value or condition |
|---|---|
| Core / material / bobbin | PQ20/16 / Magnetics-T / PCB2016FC |
| Primary / secondary turns | 45 / 8 |
| Primary / secondary wire | AWG 32 × 7 / AWG 27 × 8 |
| Calculated gap | 0.4539 mm |
| Calculated magnetizing inductance | 248.373 μH |
| Peak flux density | 0.1688 T |
| Core / primary copper / secondary copper loss | 0.1186 / 0.1442 / 0.1306 W |
| Estimated transformer total loss | 0.3933 W |
| Estimated rise / hotspot | 4.10 / 44.10 °C |
| Physical fill | 73.03% |
Scope of this run
Using adapter_24w inputs, 40°C ambient and natural cooling, the run used thermal class F, heavy insulation, non-interleaved winding and balanced ranking. The engine returned 52 candidates; the table shows the first-ranked result from this run, not a manufacturing-, insulation- or system-validated design.
Independent numerical checks
Input power is 24/0.83 = 28.916W. The magnetizing-inductance and frequency check gives a peak current of approximately 1.893A. After turns rounding, candidate D + D2 is approximately 0.767, below 1. The three magnetic-component loss terms sum to about 0.3933W.
How close is this to a physical design?
The 90–375V range is a DC bus range, not an AC input range. The 83% value is an assumed system efficiency, not a measured or proven efficiency. The 0.3933W estimate covers transformer loss, not all power-stage losses. Approximately 73% physical fill and multiple parallel strands require winding, insulation and space review. The 4.10°C rise is a thermal-model result, not a prototype temperature measurement.
Reproduction and result record
Load the named preset in the corresponding app version, check the input and winding settings, and run the core-and-winding calculation. Database, version, settings and ranking changes can affect the candidates. The public record includes inputs, selected candidates, versions and source-file hashes; it is not an app-importable project file.
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