In this article, a new single-switch buck converter (without considering the synchronous rectifier) with extended duty cycle and continuous output current is proposed. The presented converter employs a self-driven synchronous rectifier with gate energy recovery, which leads to efficiency improvement and simplicity of the converter and the gate drive circuit. The extended duty cycle results in lower current stress of the high-side MOSFET and reduced voltage stress across the synchronous rectifier. Furthermore, the reverse recovery losses of synchronous rectifier are dramatically decreased due to the applied coupled inductors. The introduced converter also provides shoot-through protection and load protection when the high-side MOSFET remains on . In order to clamp the drain–source voltage spikes of the main switch and recover the leakage inductance energy, a lossless snubber circuit is added, which reduces the turn- off drain–source voltage and consequently decreases the turn- off switching losses of the main MOSFET . Moreover, the main switch turns on under zero current switching (ZCS), which results in efficiency improvement. A 150-W prototype of the proposed converter is implemented to verify the theoretical analysis and confirm its efficiency improvement and advantages.

A High Step-Down Buck Converter With Self-Driven Synchronous Rectifier

The application of the dual-mode time-sharing technique in novel transformerless photovoltaic (PV) inverters is proposed and investigated. The simultaneous high step-down or high step-up conversion with 97.6% peak efficiency and injected current with total harmonic distortion D /(1- D ))2 and D /(1- D )2, respectively. Furthermore, a 1 kW, 220 VAC and 200 VDC experimental prototype is implemented to confirm the theoretical achievements.

/pdf/high-buck-in-buck-and-high-boost-in-boost-dual-mode-inverter-26k0udrxxq.pdf

High Buck in Buck and High Boost in Boost Dual-Mode Inverter (Hb 2 DMI)

This article presents a detailed analysis and design of a high step-down converter. The proposed converter achieves high step-down voltage gain without the need of extreme duty cycles by using coupled inductor. The converter features low switch stresses, which reduces the conduction loss by using low voltage MOSFETs. Moreover, the magnetizing current of the coupled inductor is zero, which reduces the magnetic size. The leakage energy of the coupled inductor is recycled. Zero voltage switching is achieved to reduce switching loss and improve the EMI performance. In addition, continuous output current is achieved; hence, small filtering capacitor can be used. A hardware prototype is built and experimental results verify the feasibility of the step-down converter. 

Analysis and Design of a Nonisolated High Step-Down Converter With Coupled Inductor and ZVS Operation

This article proposes a family of asymmetric high-step-down converters in which zero voltage switching (ZVS) is achieved and common ground between the input and the output is retained. The proposed converters are derived from the multiphase coupled-buck converter and both coupled inductors and series capacitors are employed in order to achieve a high-step-down conversion ratio. Therefore, the voltage stress across the freewheeling diodes and the current stress of the main switches are reduced. Furthermore, switching losses including turn- on , turn- off , capacitive turn- on , and reverse recovery losses are considerably reduced due to the soft switching of semiconductor devices. As a result, the converter can efficiently operate at higher switching frequencies. Also, in comparison to the conventional interleaved buck converter (IBC) the cost, volume, weight, and complexity of the proposed topologies have not increased significantly as the proposed converters use the minimum number of auxiliary components and, similar to the conventional IBC, share the common ground. The validity of this research is confirmed by the experimental results of a 150 V to 12 V/15 A prototype.

Asymmetric ZVS Buck Converters With High-Step-Down Conversion Ratio

High step-down nonisolated dc–dc converter with coupled inductors is proposed. The converter is used a simple lossless clamping circuit. Moreover, it produces the current ripple cancelation at the output due to series connection between the coupled inductors and the output. Automatic current sharing is done in the proposed converter even if the switches have different duty cycles. The proposed converter has lower voltage stress in comparison with traditional Buck converter and also different topologies of Buck converters with the coupled inductors. Besides, the current stress on semiconductor devices is reduced due to the interleaved structure. Finally, the converter has lower number of components in comparison with the similar structures. The mentioned advantages candidate the proposed converter to apply in photovoltaic system. A 200-W laboratory prototype converter is considered and constructed. The experimental results presented confirm the aforementioned features and theoretical analysis.

High Step-Down Nonisolated DC–DC Converter With Coupled Inductors

This paper proposes a high-step-down dc–dc converter with continuous output current which utilizes coupled-inductors. Another main feature of this converter is applying the same number of switches as the synchronous buck converter. The introduced converter is suitable for non-isolated low-voltage high-current applications, especially voltage regulator modules (VRMs) with 12-V-input. Owing to extension of the duty cycle, the main mosfet current stress and the synchronous rectifier switch voltage stress are significantly reduced. However, the discharge of the leakage inductance energy increases the main mosfet voltage stress. By employing a simple lossless clamp/snubber circuit the leakage inductance energy is recovered, the voltage spike across the main mosfet is clamped, and the turn- off switching losses are reduced. There is at least one inductor in all current paths which creates an intrinsic protection against current shoot-through and provides zero-current-switching (ZCS) turn- on for the main mosfet. High efficiency is attained by the proposed converter due to extended duty cycle, low number of switches, and soft switching operation while the converter driver is just like the conventional buck converter. Due to the single-phase structure of the proposed converter, this converter is a viable alternative to the buck VRM. Similar to the other converters using coupled-inductors, the complexity of coupled-inductors design and the space occupied by coupled-inductors can be considered as drawbacks. A prototype of the proposed converter is implemented to verify the converter operation and the theoretical analysis.

High-Step-Down DC–DC Converter With Continuous Output Current Using Coupled-Inductors

In a high-precision motion system, a position controller creates an appropriate current reference signal based on a position reference trajectory. Then, power amplifiers use this reference signal to drive actuators to translate the current reference into the desired force to move the subject to the desired position. Any imperfection in the power amplifier performance adversely affects the overall positioning system accuracy. Hence, to improve the motion system's performance, the effects of power amplifier imperfections on such high-precision systems are investigated through a complete mechatronics model that combines control, mechanical and electrical aspects. Additionally, to demonstrate how the system performance can be improved by changing the control strategy, a voltage-mode cascaded current controller is applied to the power amplifier and different feedforward strategies are applied to the position loop. We demonstrate that the accuracy of position control can be improved by a factor of five by taking into account the amplifier dynamics and controller design.

Marziyeh Hajiheidari

Papers

High-Step-Down DC–DC Converter With Continuous Output Current Using Coupled-Inductors

Asymmetric ZVS Buck Converters With High-Step-Down Conversion Ratio

Analysis of Power Amplifier Contribution to the Precision of Motion Systems