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Power Electronics Europe News
Pulisiv’s nomogram determines transformer parameters quickly

The nomogram provides a fast and accurate visual process for identifying primary side inductance and minimum duty cycle, says the company.

Nomography is a precise and practical method for calculating complicated formulae using a parallel co-ordinate system. Results are obtained quickly and reliably by simply drawing one or more lines, without needing to solve algebraic equations.

The Pulsiv nomogram consists of four steps. The first is to note the switching frequency and maximum duty cycle of a chosen flyback controller.

Next, select the required peak current (based on the output power) and minimum flyback operating voltage.

The third step addresses the primary side inductance and minimum duty cycle. Users 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).

The final step is to check the flyback controller datasheet. This is to ensure that the minimum duty cycle, calculated from step three, 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.

DCM flybacks are typically  used in low to medium power designs where isolation is required. They are often paired with a boost PFC front-end stage with significant switching losses under low load conditions and poor average efficiency.

Pulsiv OSMIUM technology uses a patented switching technique by applying intelligence to an active valley fill approach for converting AC/DC. The company said this method offers several advantages, including a front-end efficiency of 97.5 per cent, (99.5 per cent peak) and 90 per cent at 2W; a totally flat efficiency profile across the entire load range; input voltage derating and inrush current are eliminated and it extends the range of single-switch flybacks to 180W.




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