Several techniques are proposed in the literature to improve the cross-regulation performance of a multiple output flyback converter (MOFC). However, some drawbacks exist, first, inability to completely eliminate cross-regulation, second, reduction of power density due to a high number of additional components, third, increased losses. To overcome these challenges, this article presents a scheme to independently control the outputs of an MOFC, thereby achieving an excellent cross-regulation performance over a wide range of loads, without any additional switching or magnetic component. The unique gate dependent reverse conduction characteristics of gallium nitride (GaN) high electron mobility transistor is utilized to control the flow of current to each of the output capacitors. The operational principle and the steady-state analysis are provided in detail. Moreover, design considerations, such as the switching frequency, GaN gate bias, leakage inductances, and output capacitance, are discussed, focusing on their impacts on the key design goals, particularly the efficiency, power density, and output voltage ripple. Furthermore, SPICE simulations are used to demonstrate the improvement in cross-regulation over existing schemes. Finally, a 40 W dual output laboratory prototype is built to verify the analysis. The measured maximum cross-regulation is 0.2%, which validates the effectiveness of the scheme.

The recently proposed independently controlled multiple output flyback converter (ICMOFC) scheme improves cross-regulation by utilizing gallium nitride (GaN) switches with negative gate turn- off voltage. The highly inefficient reverse conduction (RC) of negative gate biased GaN devices leads to significant RC loss in the existing ICMOFC scheme. To mitigate this problem, this letter proposes a new pulsewidth modulation (PWM) scheme. The RC loss reduction is achieved by reducing the RC duration and RC current. The effectiveness of the proposed PWM strategy is analytically and experimentally verified using a 40-W dual output flyback converter. The results demonstrate a peak efficiency improvement of 1.26% over the existing ICMOFC scheme. Furthermore, the scheme also achieves high power density (51 W/in $^{3}$ ) and excellent cross-regulation (0.2%).

The conventional cascode structure for driving depletion-mode (D-mode) gallium nitride (GaN) high electron mobility transistors (HEMTs) raises reliability concerns. This is because of the possibility of the gate to source voltage of the GaN HEMT surging to a negative voltage during the turn off transition. The existing solutions for this problem in the literature produce additional drawbacks such as reducing the switching frequency or introducing many additional components. These drawbacks may outweigh the advantages of using a GaN HEMT over its silicon (Si) alternative. This paper proposes two innovative gate drive circuits for D-mode GaN HEMTs—namely the GaN-switching based cascode GaN HEMT and the modified GaN-switching based cascode GaN HEMT. In these schemes, the Si MOSFET in series with the D-mode GaN HEMT is always turned on during regular operation. The GaN HEMT is then switched on and off by using a charge pump based circuit and a conventional gate driver. Since the GaN HEMT is driven independently, the highly negative gate-to-source voltage surge during turn off is avoided, and in addition, high switching frequency operation is made possible. Only two diodes and one capacitor are used in each of the schemes. The application of the proposed circuits is experimentally demonstrated in a high voltage flyback converter, where more than 96% efficiency is obtained for 60 W output load.

Gallium nitride high electron mobility transistors outperform Silicon devices due to their excellent physical properties. However, being an immature technology, it exhibits dynamic on -state resistance ( $R_{\text{ds}, \text{on}}$ ). This causes increased conduction loss and leads to reduced operating efficiency. To evaluate the dynamic $R_{\text{ds}, \text{on}}$ of the device, a measurement circuit is required. In literature, a standardized double pulse test is widely used for the measurement of $R_{\text{ds}, \text{on}}$ . However, due to the uncontrolled off -state time and inability to independently adjust, the test conditions result in restricted measurement. This article proposes a measurement circuit of the device in power electronics operations. The circuit uses an H-Bridge-derived topology with capacitive storage to enable forward and reverse conduction mode measurement of the device. In all the modes, the circuit allows measurement from the first switching cycle and independent control over the testing conditions by using a hysteresis current control. The proposed measurement circuit is validated using simulation and experimentation. Finally, analytical efficiency compared with the state-of-the-art measurement circuits is provided.

This paper proposes a control scheme for a 3- level NPC inverter used in a grid connected PV system. The proposed scheme is useful in such way that the active and reactive power can be controlled separately. Such a scheme is applied in the rotating reference frame. The transformation of three-phase quantities (voltage and current) in to rotating reference frame is done by using Clarke and Park transformations. Controllers are designed for both voltage and current. A Space vector modulation scheme is implemented and the DC link capacitor voltages are balanced by appropriate choice of switching sequence by the space vector modulation scheme. The proposed controller is designed with Bode plot and the performance parameters of the overall system have been analyzed. The independent control of active and reactive power for different value of solar insolation is also verified.