Diode Snubber Research Articles

Design and Implementation of a Flyback-Assisted Wide-Range Fully Soft-Switched T-Type Inverter

A novel soft-switched three-level T-type inverter (3LT <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> I) is proposed in this paper. The proposed inverter provides turning-on by zero voltage transition (ZVT) and turning-off by zero voltage switching (ZVS) for main switches without any voltage or current stresses. The switching energies are transferred to the snubber capacitors, so the turning-off process of the main switches is improved by these snubber capacitors. Besides, the auxiliary switches are turned on by zero current switching (ZCS) and turned off by ZVS. Furthermore, all snubber diodes are operated by soft switching (SS), and the proposed SS snubber cell decreases the electromagnetic interference (EMI) noises. The novel snubber cell has a simple structure, ease of application, common-ground switches, and low-cost features. The theoretical analysis of the inverter is clarified, and the operating modes for steady-state analysis are presented in detail. The experimental results rated 1 kW output power and 100 kHz switching frequency are provided to justify the theoretical analysis. The proposed unique snubber cell can be easily implemented in other three-level inverters (3LIs), and the practice is demonstrated in the paper.

Implementation of Snubber Circuits in a PV-Based Off-Grid Electric Vehicle Charging Station—Comparative Case Studies

With the penetration of electric vehicles (EVs), there have been paradigm shifts in the transportation sector. EVs are ideally considered to be clean and eco-friendly, but they can overload the existing grid infrastructure and significantly contribute towards carbon emissions depending on the source of charging. The ideal solution is to develop a charging infrastructure for EVs that is integrated with solar energy technology. This paper presents the design of a zero-voltage switching snubber-based bidirectional converter for an off-grid charging station for EVs. The proposed system includes a solar array with a boost converter, a bidirectional converter with snubber circuits and an energy storage unit. A comprehensive comparison between various types of snubbers, such as the resistive capacitive diode snubber, active clamp snubber and flyback snubber, is presented. This type of system configuration clamps the rail voltage, due to the difference in current between leakage inductance and low voltage side-fed inductor currents, resulting in reduced current spikes at the converter’s switches. Such a converter, therefore, leads to higher efficiency of the charging station for EVs. The design of a snubber-based off-grid charging station for EVs is formulated and validated in the MATLAB/Simulink environment.

Phase-Shifted Full-Bridge DC–DC Converter With High Efficiency and High Power Density Using Center-Tapped Clamp Circuit for Battery Charging in Electric Vehicles

In this paper, a phase-shifted full-bridge (PSFB) converter employing a new center-tapped clamp circuit is proposed to achieve high efficiency and high power density in electric-vehicle battery charger applications. By using a simple center-tapped clamp circuit, which consists of two diodes and one capacitor, many limitations in conventional PSFB converters are solved. The proposed center-tapped clamp circuit provides the clamping path and allows the secondary voltage stress to be clamped to the secondary-reflected input voltage. This results in a greatly reduced conduction loss in the secondary full-bridge rectifier (FBR) due to the low-forward-voltage drop of low-voltage-rated diodes, and the resistor–capacitor–diode snubber loss is eliminated. In addition, the circulating current in the primary side is removed without any duty-cycle loss. Furthermore, the turn- off switching loss in the FBR is substantially reduced due to the decreased reverse-recovery current and the reduced reverse voltage. With these advantages, high efficiency can be achieved. Besides, the size of the output inductor is considerably reduced with the aid of clamping voltage, resulting in a high power density with saving the cost. In order to confirm the effectiveness of the proposed converter, a 3.3-kW prototype was tested. Experimental results show that the proposed converter achieves high efficiency over the entire conditions with high power density.

High Step-Up Coupled-Inductor Cascade Boost DC–DC Converter With Lossless Passive Snubber

In this paper, a high step-up coupled-inductor cascade boost dc–dc converter with lossless passive snubber is proposed. Although a conventional cascade boost converter has larger voltage gain compared to a boost converter, it is still not suitable for high step-up voltage conversion. In the proposed converter, a coupled inductor is adopted for the cascaded boost converter to further increase the voltage gain. However, a leakage inductance of the coupled inductor causes a high voltage spike at a main switch. A resistor–capacitor–diode snubber is commonly used to simply solve this problem, but it is also the cause of additional power loss. Therefore, the lossless passive snubber is suggested in this paper in order to prevent efficiency drop by a snubber circuit. In conclusion, the proposed converter has high voltage gain and improved power efficiency. Experimental results from an output 400-V 200-W prototype at a constant switching frequency of 50 kHz are presented to verify the performance of the proposed converter.

A Novel Soft-Switching Full-Bridge Converter With a Combination of a Secondary Switch and a Nondissipative Snubber

In this paper, a novel soft-switching full-bridge converter with an additional secondary switch and a nondissipative energy recovery snubber is proposed. Thanks to the combination of an active switch and the capacitor—diode–diode snubber employed at the secondary side of the converter, the proposed converter can achieve zero-voltage zero-current switching for all of the primary switches and rectifier diodes over the entire load range. As a result, the rectifier diodes have no reverse-recovery problem and their ringing voltage is clamped. In addition, since no phase shift is used for the gate signals of the primary-side switches, the converter control can be implemented easily and it has no circulating current inherently. The converter exhibits a significant improvement in terms of efficiency, especially under light-load conditions, which is difficult to achieve with conventional phase-shift full-bridge converters. A 3-kW prototype circuit is implemented to verify the superior performance of the proposed converter.

A High-Switching-Frequency Flyback Converter in Resonant Mode

The demand of miniaturization of power systems has accelerated the research on high-switching-frequency power converters. A flyback converter in resonant mode that features low switching losses, less transformer losses, and low switching noise at high switching frequency is investigated in this paper as an alternative to a conventional quasi-resonant (QR) flyback topology to increase power density. In order to find a compromise between magnet size, electromagnetic interference (EMI), and efficiency, the concept utilizes the resonant behavior between transformer leakage inductance and snubber capacitor to achieve near-zero-voltage switching at both turn-on and turn-off of the primary switch, low core loss due to a continuous transformer magnetizing current, and reduced EMI due to low di / dt and dv / dt values. Meanwhile, the concept uses the regenerative snubber to recycle the transformer leakage energy with two snubber diodes and one snubber capacitor. The proposed concept has been validated on a 340-kHz 65-W prototype. Compared to the conventional QR flyback converter operating at the same switching frequency, the proposed concept has 2% efficiency improvement and better EMI performance.

A High-Voltage Solid-State Switch Based on Series Connection of IGBTs for PEF Applications

Pulsed electric field (PEF) technology is a promising nonthermal processing techniques that can be utilized to inactivate microorganisms in liquid food with high-voltage PEF. Herein, a high-voltage solid-state switch consisting of 64 insulated gate bipolar transistors (IGBTs) connected in series was designed and developed for the PEF treatment. Regarding the unbalanced sharing of voltage in series-connected IGBTs, the resistor–capacitor–diode snubber circuit was specifically used and investigated in terms of model of parameters. Furthermore, using gate drivers and optic fiber, the driving circuit and protection circuit were designed and validated. A 50-kV isolation level power supply was built in order to provide 16 independent IGBT stacks with 24 V of power each. The results show that the developed switch works adequately a delay time of 380 ns with 35.8-kV voltage and 44.8-A current capacity. Moreover, the response time of the short-circuit protection is acceptable as well with a reaction time of under $7~\mu \text{s}$ . In conclusion, the switch designed for PEF treatment of liquid food performs within set parameters and is ready for pilot-scale processing capability.

Soft-Switching Dual-Flyback DC–DC Converter With Improved Efficiency and Reduced Output Ripple Current

This paper presents a soft-switching dual-flyback dc-dc converter with improved efficiency and reduced output ripple current. Zero-voltage-switching (ZVS) technique and a dual-flyback module for reducing the number of snubber current paths are adopted to improve efficiency. For the ZVS technique, a self-driven synchronous rectifier (SR) is used instead of an output diode. By turning the self-driven SR off after a short delay, a main switch is turned on under the ZVS condition. For reducing the number of snubber current paths, a dual-flyback module and a snubber diode are used. When the main switch is turned off, leakage inductance energy is absorbed by a snubber diode into an input source and a primary dc-bus capacitor. Then, this energy is reprocessed by the dual-flyback dc-dc module to secondary side. Hence, there is only one snubber current path. In addition, the proposed converter features a reduced output ripple current because of the continuous current. Consequently, the proposed converter can achieve high efficiency and reduced output ripple current. To verify the performance of the proposed converter, operating principles, steady-state analyses, and experimental results from a 340 to 24-V, 100-W prototype are presented.

Single-Stage Single-Switch AC-DC LED Driver with High Power Factor

A single-stage single-switch AC-DC LED driver with high power factor is proposed to overcome the drawbacks of the conventional boost-flyback PFC LED driver. In the proposed LED driver, the boost PFC converter with discontinuous conduction mode (DCM) is adopted to achieve high power factor and the modified flyback DC-DC converter with dual input is integrated to provide electrical isolation and the regulated output voltage. In order to divide input of DC-DC module (dc-link capacitor), the transformer with dual-primary winding is used. Moreover, the leakage inductor currents are absorbed by the dc-link capacitors through a snubber diode and the maximum voltage stress is limited to double DC-link voltage. Therefore, there are virtually no conduction losses by snubber circuit. In additional, some input power is directly transferred to the load and the remaining power is stored in dc-link capacitor. Hence, the total power efficiency is improved. The presented theoretical analysis is verified by prototype of 50kHz and 80W converter.

A PSFB-Based Integrated PEV Onboard Charger With Extended ZVS Range and Zero Duty Cycle Loss

A conventional phase-shift full-bridge (PSFB) converter suffers from easy failure of zero-voltage switching (ZVS) in the lagging leg under light load conditions. This poses a significant challenge to the optimal design of PSFB-based plug-in electric vehicle (PEV) onboard chargers. In this paper, a self-reconfigured integrated onboard charger architecture is proposed for PEVs to cope with this design challenge. In this architecture, the PSFB converter is adopted as the main topology to charge the high-voltage battery pack, while the half-bridge LLC resonant converter is employed to charge the low-voltage auxiliary battery. Under light-charging mode, the half-bridge LLC converter is reconfigured to be paralleled with the PSFB topology to guarantee the ZVS of the lagging leg mosfet s. Moreover, a capacitor–diode–diode snubber is added to resolve the duty cycle loss issue of the PSFB converter and to reduce the circulating current. Practical design considerations are presented for both the PSFB and the half-bridge LLC converters. Frequency modulation and the phase-shift modulation provide two degrees of freedom to regulate the output voltage/current of both converters. The proposed charger architecture maintains low cost and high efficiency in this specific application. A 390 V input, 420 V/2.4 A, 14 V/21 A outputs, 1.3 kW rated converter prototype is designed, analyzed, and tested to verify the proof of concept.

Efficient Single-Switch Boost-Dual-Input Flyback PFC Converter With Reduced Switching Loss

This paper presents an efficient single-switch boost-dual-input flyback power factor correction (PFC) converter. To achieve a high power factor, a boost PFC cell operating in discontinuous conduction mode is presented. A dual-input flyback dc–dc module, which consists of parallel primary windings and serial secondary windings, operating in critical conduction mode is introduced for galvanic isolation and valley-switching operation. In addition, the proposed converter features high efficiency because the input power is equally divided, and some power is directly transferred to the load by the dual-input flyback dc–dc module. The remaining power is stored in dc-bus capacitors, and it is closely related to the holdup time. Moreover, the currents in the leakage inductors are absorbed by the dc-bus capacitors through a snubber diode, and they are reprocessed by the dual-input flyback dc–dc module. Consequently, the peak voltage in the MOSFET drain is clamped, and the total power conversion efficiency is improved. To verify the performance of the proposed converter, the operating principles, steady-state analysis, and experimental results from a 48 V, 100 W prototype are presented.

Design and Implementation of Self-Oscillating Flyback Converter With Efficiency Enhancement Mechanisms

This paper presents a self-oscillating flyback converter with efficiency enhancement mechanisms using lossless snubber and the energy recovery winding. The conventional self-oscillating flyback converter with resistor–capacitor–diode snubber has the issues of low conversion efficiency and high no-load power loss. Furthermore, in order to fulfill the $95 \mbox{V}_{\mathrm{p-p}}$ voltage limitation of the IEC62684 Common-Mode (CM) Standard, the parasitic capacitor of a transformer between the primary and secondary windings has to be reduced, which leads to large leakage inductance for the transformer. However, the larger leakage inductance stores more energy to cause the high voltage spike on the main switch during the turnoff transition period. Therefore, the lossless snubber is employed to suppress the voltage spike and increase the conversion efficiency. In order to increase more conversion efficiency, the energy recovery winding is employed to recycle the energy discharged from the gate–source capacitor of the main switch. Furthermore, the burst-mode control mechanism is utilized to reduce the power consumption at the no-load and light-load conditions. Finally, a prototype circuit of the 7.5-W self-oscillating flyback converter with efficiency enhancement mechanisms is built to verify the performance feasibility, such as the CM voltage, the voltage stress on the switch, the conversion efficiency, and the no-load power loss.

Analysis of EMI Radiation Noise from a Novel Passive Energy Recovery type Soft Switching Circuit

High dv/dt rate at switching of IGBTs become source of EMI noise. For this problem, various methods that makes low dv/dt rate by using soft switching circuit are proposing. In this paper, a novel snubber circuit with passive energy recovery for soft switching inverter is proposed. This novel circuit uses a capacitor which makes zero voltage switching to both upper and lower IGBTs, and a transformer which regenerates the snubber energy. And this paper describes the EMI noise from the novel soft switching circuit. From results of experiment and analysis, we clarified that radiational noise is not reduced by making low dv/dt rate of only IGBT. Radiational noise generates from resonant current flowing through the soft switching circuit and IGBT. This resonant current don't flow trough the conventional hard switching circuit. So, we indicate the reducing methods of radiational noise that the reducing the resonant current by using saturation type reactor and RC snubber with snubber diodes. The effect of the methods has been verified by experimental and simulational results.

Techniques for reduction of required headroom in high-frequency magamp postregulators

High headroom in a magamp postregulator increases circuit losses, including power transistor losses, saturable reactor core loss, and freewheeling diode snubber loss. Higher headroom also requires the use of higher voltage diodes. The authors describe common causes for large headroom requirement and discuss various techniques to reduce it.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Computer-aided design of power transistor inverter snubber circuits

The conventional voltage-source inverter snubber circuit has been examined in detail by computer simulations. A new snubber arrangement is proposed and analysed. It aims to reduce the transient voltage overshoot without incurring excessive switching losses. Also, the reverse-recovery processes of the snubber diodes are controlled so that the requirement for fast snubber diodes is not mandatory. Computer simulations by the program SPICE have been used throughout the analysis and design process, and hence have been proved to be a useful design tool.

Arbitrary space charge to bulk boundary model of Auger recombination for semiconductor power diodes

An arbitrary semiconductor junction is used to obtain an equation for junction current density in terms of the conditions at the boundaries between the space charge and the quasineutral bulk regions on each side of the junction. Included are the effects of recombination in the space charge volume as well as bandgap narrowing and ambipolar diffusion effects in the bulk regions at these boundaries. The equation also accounts for the effects of drift field, which is neglected in other theories, and demonstrates that it exerts a form of cross-coupled modulation upon current flow. Under certain conditions, it may be shown that the current density is largely determined by the carrier density gradient at the space charge to bulk boundaries. A solution for carrier density gradient, which is obtained by one integration of the diffusion equation, does not require a precise solution for carrier density profile and may be used to model bulk region Auger recombination with the aid of the derived equation for current density. This contribution may find use in the design of snubber diodes.