I. Introduction
The leakage inductance of a high-frequency transformer plays a crucial role in diverse isolated dc/dc converters, as its accuracy affects the control and performance of converters. For example, in a dual active bridge (DAB) converter, the primary leakage inductance is in series with an inductor, which affects the zero-voltage switching of the converter and that should be taken into consideration during the design process [1]. In addition, the inductor in series with the transformer can also be integrated into the transformer to improve the power density of DAB, which depends on the accurate calculation of leakage inductance [2]–[4]. Besides, in isolated dc/dc converters, when the transformer does not accompany the series inductor, the leakage inductance should be accurately controlled. On the one hand, if the leakage inductance is too large, a lot of energy stored in the transformer during operation will cause a large spike voltage at the moment when the switch is being turned off, causing an over-voltage breakdown on the switch. On the other hand, there is a voltage drop when the current flows through the large leakage inductance, leading to the decline of the transformer gain [5], [6]. Thus, the accurate calculation of leakage inductance is of great significance for the operating mode and performance of converters.