Nomograms
What is a Nomogram?
Nomography was first invented in 1884 by French engineer Philbert Maurice d’Ocagne to provide engineers with a precise and practical method for calculating complicated formulas using a parallel coordinate system. Results from a nomogram are obtained quickly and reliably by simply drawing one or more lines without needing to solve algebraic equations.
Why use a Nomogram?
A number of key parameters must be determined before designing power supplies that incorporate a Flyback converter and Nomograms developed by Pulsiv can be used to simplify this process. Pulsiv OSMIUM technology can improve the efficiency of Flyback converters by reducing the peak operating voltage.
As a result:
- Primary side inductance is reduced
- Leakage inductance is lowered
- Total winding area is increased
This enables engineers to select a smaller transformer core size while reducing overall weight and cost.
To view and download the Pulsiv Nomograms, please click below:
Calculating primary side inductance for a DCM Flyback (click to open)
To use this Nomogram effectively, it is essential to understand certain parameters in advance of starting the design.
- Step 1: Switching frequency & maximum duty cycle
Note the Switching Frequency and Maximum Duty Cycle of your chosen Flyback controller.
- Step 2: Peak current & minimum operating voltage
Select the required Peak Current (based on the output power) and Minimum Flyback Operating Voltage.
- Step 3: Primary side inductance & minimum duty cycle
Draw straight lines across the Nomogram to identify suitable values for Primary Side Inductance (for the DCM Flyback) and Minimum Duty Cycle (based on the maximum Flyback operating voltage).
- Step 4: Check the flyback controller datasheet
It is important to check the Flyback controller datasheet to ensure that the meet the minimum duty cycle, calculated from Step 3, can be achieved. Some controllers change the switching frequency based on the operating voltage of the Flyback and this must be considered when using the Nomogram to determine the Minimum Duty Cycle.
The video below provides an example of how to use this Nomogram