Is the leakage inductance of the switching power supply transformer included in the total inductance

Is the leakage inductance of the switching power supply transformer included in the total inductance? How to measure the leakage inductance and inductance value of a transformer?

Regarding the leakage inductance of switching power supply transformer, we need to first clarify some basic concepts.

What is leakage inductance?

Leakage inductance is also called magnetic leakage inductance or magnetic dispersion coefficient. It refers to the main magnetic flux that occurs in the transformer due to the different number of coils and arrangement of the coils in the winding. A part of the magnetic flux cannot pass through the winding and leak out due to the reason. This leaked flux is conducted through the air surrounding the magnetic material or the air in the surrounding material.

The relationship between leakage inductance and total inductance

The total inductance refers to the total amount of magnetic energy that can be stored in the winding of the transformer. It is composed of the main magnetic flux and the leakage magnetic flux. decided jointly. In a transformer, the main magnetic flux and the leakage flux interact, so the leakage inductance is included in the total inductance.

Measurement of transformer leakage inductance and inductance values

Transformer leakage inductance and inductance values can be measured by the following methods:

1. LCR bridge method
The LCR bridge method is an indirect method of measuring inductance and is based on a simple small circuit of neurons.

When measuring, first connect the measuring inductor and the known capacitor in parallel to form a resonant circuit. Then take a reading at the resonant frequency point and calculate the inductance value through the circuit parameters.

This method is relatively simple, but the accuracy is relatively low.

2. Differential method

The differential method is a high-precision measurement method that determines the inductance value by measuring the voltage drawn at both ends of the winding.

During measurement, the frequency of the current in the circuit is constantly changed, and the voltages at both ends at different frequencies are recorded. Then use a differentiator instead of an oscilloscope to calculate the phase difference between the two ends to obtain the inductance value.

This method is more accurate, but requires the use of some high-precision instruments.

3. Theoretical calculation method

Theoretical calculation method is a method of calculating the inductance value through theoretical formulas.

For simple coils, the inductance value can be calculated directly using formulas such as Ohm's law. However, for complex structures such as transformers, more complex calculation methods, such as finite element analysis, need to be used.

This method can obtain more accurate results, but requires a certain background knowledge in mathematics and physics.


In short, leakage inductance is an inevitable phenomenon in transformers and can be measured by various methods. In practical applications, understanding the characteristics of leakage inductance and its impact on circuits can help us better design and optimize circuits such as switching power supplies.