Flyback Converter Calculator
Calculate turns ratio and duty cycle for flyback (isolated) DC-DC converters
Volts (V)
Volts (V)
Percentage (%) - Leave empty to calculate duty cycle
How to Use This Calculator
Enter Input and Output Voltages
Enter the DC input voltage and desired output voltage in volts. These are the primary parameters for flyback converter design.
Enter Duty Cycle (Optional)
If you know the duty cycle, enter it as a percentage. The calculator will then determine the required transformer turns ratio. Leave empty to calculate duty cycle instead.
Get Results
Click calculate to see either the required turns ratio (if duty cycle provided) or the calculated duty cycle (if left empty).
Formula
Vout = (Vin × N × D) / (1 - D)
Where:
- Vout = Output voltage (V)
- Vin = Input voltage (V)
- N = Transformer turns ratio (Secondary:Primary)
- D = Duty cycle (as decimal, 0 to 1)
Solving for Turns Ratio:
N = (Vout × (1 - D)) / (Vin × D)
Example 1:
Input = 12 V, Output = 5 V, Duty Cycle = 50%
N = (5 × (1 - 0.5)) / (12 × 0.5) = 2.5 / 6 = 0.417:1
Example 2:
Input = 24 V, Output = 12 V, Duty Cycle = 40%
N = (12 × 0.6) / (24 × 0.4) = 7.2 / 9.6 = 0.75:1
About Flyback Converter Calculator
The Flyback Converter Calculator is a free online tool that helps you design flyback (isolated) DC-DC converters. Flyback converters use a transformer to provide electrical isolation between input and output, making them ideal for applications requiring safety isolation or multiple output voltages. This calculator determines the required transformer turns ratio and duty cycle for your voltage conversion requirements.
When to Use This Calculator
- Isolated Power Supplies: Design isolated DC-DC converters for safety and noise isolation
- Multiple Outputs: Design converters with multiple isolated output voltages
- AC-DC Adapters: Calculate transformer parameters for wall adapters and chargers
- High Voltage Applications: Design isolated converters for high voltage applications
- Educational Purposes: Learn about flyback converter design and transformer calculations
Why Use Our Calculator?
- ✅ Accurate Calculations: Uses the correct flyback converter formula
- ✅ Flexible: Calculate either turns ratio or duty cycle
- ✅ Easy to Use: Simple interface requiring voltages and optional duty cycle
- ✅ Isolation Design: Helps design isolated power supplies
- ✅ Free Tool: No registration or payment required
- ✅ Educational: Includes formulas and examples for learning
Common Applications
Wall Adapters: Phone chargers and laptop adapters use flyback converters to provide isolated, regulated DC output from AC mains. A typical design might convert 120V AC to 5V DC with complete isolation for safety.
Multiple Output Power Supplies: Flyback converters can provide multiple isolated outputs using multiple transformer windings. This is common in computer power supplies where different voltages (3.3V, 5V, 12V) are needed.
High Voltage Applications: Flyback converters can step up voltage significantly using transformer turns ratio. This is used in high voltage power supplies, neon sign drivers, and CRT displays.
Battery Chargers: Isolated battery chargers use flyback converters to provide safe, isolated charging current. The isolation protects users from high voltage on the input side.
Tips for Accurate Results
- Enter voltages in volts (V)
- Duty cycle should be between 0% and 100% (but not exactly 100%)
- Turns ratio is Secondary:Primary (N:1)
- Flyback converters can step up or step down voltage depending on turns ratio
- Consider efficiency losses - actual output may be 5-15% lower
- Transformer design also depends on power level and switching frequency
- Ensure duty cycle allows sufficient off-time for transformer reset
Frequently Asked Questions
What is a flyback converter?
A flyback converter is an isolated DC-DC converter that uses a transformer to store energy during the switch-on phase and transfer it to the output during the switch-off phase. It provides electrical isolation between input and output, making it safe for direct connection to AC mains.
How is flyback different from forward converter?
Flyback converters store energy in the transformer during ON time and transfer it during OFF time. Forward converters transfer energy directly during ON time. Flyback is simpler but typically lower power, while forward is more efficient for higher power applications.
Can flyback converters step up or step down voltage?
Yes, flyback converters can both step up and step down voltage depending on the transformer turns ratio. If N > 1, it steps up. If N < 1, it steps down. The formula allows for both configurations.
What is the typical efficiency of flyback converters?
Flyback converter efficiency typically ranges from 75-90%, depending on power level, switching frequency, and component selection. Lower power converters (< 10W) tend to have lower efficiency, while higher power designs can achieve 85-90% efficiency.
Do I need to consider transformer reset?
Yes, flyback converters require transformer reset during the OFF time. The duty cycle must allow sufficient time for the transformer core to reset. Maximum duty cycle is typically limited to 50% for single-switch flyback or 50% per switch for two-switch flyback designs.