Skip to main content

Discontinuous Conduction Flyback Transformer Primary Inductance Calculator

Unlike conventional transformers, a flyback coupled inductor stores energy in its magnetic core during switch ON-time and releases it to the output during OFF-time.

Minimum or nominal DC bus input

Total secondary load power

PWM switching frequency

Nominal peak duty ratio

Calculated Result
44.1 µH

Primary Inductance (Lm)

Peak Primary Current

4.9 A

Calculation Breakdown

  1. DCM Energy BalanceLm = (Vin² · D²) / (2 · Pin · fsw) => 44.1 µH

Inductance vs Frequency

Interactive visualization based on your current inputs

Lm
0.01428425565 kHz100 kHz150 kHzSwitching FreqInductance (µH)

What Is the Discontinuous Conduction Flyback Transformer Primary Inductance Calculator?

Unlike conventional transformers, a flyback coupled inductor stores energy in its magnetic core during switch ON-time and releases it to the output during OFF-time.

Designing for discontinuous conduction mode (DCM) ensures complete core demagnetization and simplifies control loop compensation.

How Does the Discontinuous Conduction Flyback Transformer Primary Inductance Calculator Work?

The calculation evaluates user-provided measurements using recognized domain equations, converts between measurement units, and adjusts for real-world efficiency factors.

Discontinuous Conduction Flyback Transformer Primary Inductance Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

L_m = \frac{V_{in}^2 D^2}{2 P_{in} f_{sw}}, \quad I_{pk} = \frac{V_{in} D}{L_m f_{sw}}

DCM energy transfer inductance and peak switch current.

How to Use the Discontinuous Conduction Flyback Transformer Primary Inductance Calculator

  1. Enter your primary measurements in the input fields above.
  2. Select your preferred units (e.g. metric or imperial) if applicable.
  3. Review or adjust operational assumptions such as field efficiency.
  4. Click Calculate to instantly generate the full results breakdown and visual chart.
  5. Use the Reset button at any time to clear the form and test a new scenario.

Step-by-Step Example Calculation

PoE 45W Isolated Converter

Input Values:

inputVoltageVin:48.0
outputPowerPoWatts:45.0
switchingFreqKhz:130.0
dutyCycleD:0.42

Understanding Your Result

Your calculated result represents the realistic operational capacity or baseline output under the specified conditions. Comparing theoretical and effective outputs reveals the direct impact of turns, overlap, and practical downtime.

Factors That Affect the Result

Field terrain, operator experience, equipment maintenance, overlap margin, and weather conditions can significantly influence real-world output.

When Should You Use This Calculator?

Use this calculator whenever you need quick, verified estimates for job planning, budgeting, equipment sizing, or project timelines.

Assumptions & Limitations

  • Assumes 85% typical conversion efficiency for primary energy balance.

Frequently Asked Questions

Calculation Accuracy & Reference Note

This calculator implements verified, deterministic mathematical equations based on published standards. Results should be treated as professional engineering estimates; always verify critical operations with local equipment manuals and site inspections.

Explore more tools and calculators in Math Calculators