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In order to reduce the conduction loss of diode, synchronous rectification is usually adopted in very-high-frequency (VHF) converters, in which the rectifier diode is replaced by a mosfet with very low on-state resistance. And to ensure normal operation of the synchronous rectifier switch, it is necessary to design a suitable driver with accurate timing. The widely used self-oscillating resonant drive circuit has a limited range of duty cycle adjustment, and the body diode of synchronous rectifier switch has long on-state time and a large conduction loss. Therefore, based on the analysis and parameters optimization of matching network, a shared external drive circuit is put forward. That is, the drive signals of the inverter switch and the synchronous rectifier switch come from the same external oscillation signal. On the premise of ensuring accurate drive timing, it can improve the drive signal's duty cycle of synchronous rectifier switch, reduce the conduction loss of body diode, and improve the efficiency of converter. Then, on the basis of the proposed drive circuit, a VHF converter prototype with operating frequency of 10 MHz, 13 V input, and 8 V/10 W output is designed, and the feasibility of the proposed drive circuit is verified by simulations together with experiments.

Benefited from harmonics well-defined and easy design of filter, the ON-OFF voltage-mode control strategy suitable for the very-high-frequency (VHF, 30~300MHz) dc-dc converter has been developed in recent year. However, the potential risk of this control strategy is that unreasonable parameter design will lead to system instability. Moreover, the conventional stability methods are also difficult to adopt in VHF converters due to its feature of high circuit order and many operating modes as well as extremely high switching frequency. Hence, this article proposes a new stability analysis method suitable for VHF converter employing the ON-OFF voltage-mode control strategy. Firstly, the combined characteristic of short-period switching signal and long-period modulation signal is considered, which dividing the VHF converter into short-period open-loop system and long-period closed-loop system. Then, by establishing both system discrete iterative map models, the effect of converter and controller parameters on stability are revealed by using bifurcation diagram and eigenvalue locus as well as Jacobian matrix. As a result, the established system models and stability analysis can obtain the stability boundary and predict the nonlinear behavior, which helps to guide the parameters design to ensure system stability. Finally, experimental results evaluated the correctness of the theoretical analysis.

As an emerging technology for power demand side management, electric spring (ES) is used to improve the power quality of the grid containing a high proportion of renewable energy sources (RES). Most of the existing ESs are connected in series with noncritical loads (NCL) to form smart loads, whose power consumption can follow the variation of RES power generation automatically. However, the structure of the direct series connection between ES and NCL limits the operating range of ES. In order to solve this problem, an improved ES topology based on dual inverters, called DI-ES, is proposed. The structure of the dual inverters allows DI-ES to have two output ports, one of which is connected in series with NCL for reactive power compensation and the other output port is connected in parallel with the NCL for active power compensation. DI-ES changes the traditional structure of ES in series with NCL, and improves the power compensation capability and flexibility of ES. In this work, the topology, operating principle, and control method of DI-ES are introduced in detail. The effectiveness of DI-ES has been verified by simulation and experiment results.

By combining the existing very-high-frequency (VHF) dc/dc converter and resonant switched capacitor (SC) techniques, this article proposes a VHF dual-channel light-emitting diode (LED) driver with capacitive current balance. Unlike the conventional capacitive current-balancing LED drivers, the proposed one has higher power density, and no current spike occurred at the switching moment. Due to the problem of higher voltage stress on the diode in resonant operation for the existing VHF LED drivers, the proposed one makes both diodes that are alternately turned on clamp to each other by extending one more LED channel without adding any resonant components. As a result, the voltage stress on diode can be reduced to the total dc output voltage, which is beneficial for selecting switching components. In addition, the parasitic capacitance of both diodes can be a part of the required capacitor regardless of their inconsistency, which means that they can be absorbed by one discrete capacitor and further promote power density. The analysis and design consideration of the proposed LED driver are studied in detail. With the on–off control strategy, the feasibility and theoretical analysis are experimentally verified with a rated output power of 12 W dual-channel prototype.

In this article, the effect of the pulsewidth-modulation (PWM) delay on the stability of PWM dc–dc converters is analyzed. First, a unified frequency-domain model considering the PWM delay is proposed. Based on the proposed model, the physical mechanism of the PWM delay is the sampling characteristic of the modulation process rather than the digital controller. As the analog PWM (APWM) and digital PWM (DPWM) converters both have the modulation process, they both have the PWM delay. Then, the different stabilities of APWM and DPWM converters are compared, which are caused by the state feedback introduced by the output ripple in the APWM converter. As these differences are not caused by the additional time delay in the DPWM converter, when other parameters are the same, the DPWM converter is not always more unstable than the APWM converter. These influences are rarely reported in existing analyses of the modulation and can only be reflected by the proposed model. Finally, the stability of basic converters is analyzed by the proposed model. Compared with existing models, only the proposed model can reflect the different stabilities between the APWM and DPWM converters accurately, which is ensured by experiment results.

Parameter design is the premise to ensure the optimal performance of power electronic converters, which depends on the accuracy of the established model. However, there are still many issues for improvements in modeling methods for the parameter design of power electronic converters. Due to the lack of key mechanism and the uncertainty of parameters, the existing modeling method shows poor accuracy or efficiency. In order to simplify the process and improve the accuracy of the existing modeling method, this article proposes a hybrid data-mechanism modeling (HDMM) method for power loss of a typical power electronic converter, boost converter, which is with UC3842 control chip. Based on the main loss from inductor, switch tube, diode, and sampling resistance, the mechanism power loss modeling of boost converter is built. Besides, the artificial neural network (ANN) is used to learn from the sampled data and train the data-driven model. To improve the accuracy of the mechanism model, the HDMM for power loss of boost converter is established by modification of data-driven model with limited data. Through the proposed HDMM method, the mechanism modeling method and data-driven method are well combined and the HDMM has the advantage of high accuracy and strong generalization. In the end of this article, the feasibility and accuracy of the proposed HDMM method have been verified by hardware experiments.

This article presents a new resonant boost dc–dc converter suitable for operation at very high frequency (VHF). It consists of a series-parallel Class E inverter and a conventional Class E rectifier. The series-parallel Class E inverter operated alternately in series and parallel manner can achieve higher ac voltage, while the rectifier is responsible for forming a dc voltage to supply to the load. Whilst improving the voltage boosting capability and output power range, the proposed converter also has simpler drive structure with synchronous drive method. Compared with the existing VHF converters, the boost factor of the proposed inverter stage is increased to 2.06, which results in lower switching current stress and power losses for its converter. This is beneficial to select switching components and improve the power density. The analysis, simulation and experiment indicate that the proposed converter is suitable for wide output power range applications, such as wireless power transmission and renewable energy source. Finally, its feasibility and performance are also experimentally evaluated by a 30 MHz prototype with rated power of 20 W, and its measured efficiency as well as voltage gain are up to 80.1% and 2.81, respectively.