**4. Experimental Results**

#### *4.1. Description of the Experimental Prototype*

A 300 W prototype was built to demonstrate the feasibility of the proposed converter. The parameters and components used in the setup are listed in Table 1. The converter is designed for the target operating range shown in Figure 7b, which suits the PV applications and is similar to the previous studies [18–20]. Only generic Si MOSFETs are used in the input side to reduce the converter cost. The use of SiC devices at the output side is unavoidable due to high switching frequency.

The isolating transformer was built on an ETD39 core of 3C95 ferrite material. The transformer turns ratio *n* = 6 yields the output voltage of 350 V according to (18), which results in the boost mode at the input voltage below 30 V. The value of the output voltage is suitable for the integration with residential DC microgrids. The number of primary and secondary turns equals 9 and 54, respectively. This design yields the maximum flux density of the core of 60 mT in the worst case. Therefore, the core losses can be minimized. To reduce the skin e ffect and proximity losses in the transformer, 90 × 0.2 and 90 × 0.1 litz wires were used for the primary and secondary windings, respectively. They were interleaved to reduce the leakage inductance and insulated by the Kapton polyimide tape to minimize the capacitance between the layers. An external inductor was connected in series with the secondary winding of the transformer to increase the resonance inductance. The resonance frequency of the converter was aimed close to the switching frequency to ensure the ZVS of the primary-side MOSFETs [9]. The dead-time period between *S*1, *S*2 or *S*3, *S*4 equaled 190 ns. The PWM control signals were generated using the low-cost microcontroller STM32F334. The system e fficiency was measured by a Yokogawa WT1800 precision power analyzer.

$$m = \frac{V\_{OUT}}{2V\_{INm}}.\tag{18}$$


