Secondary Diodes Research Articles

On Automatic Resonant Frequency Tracking in LLC Series Resonant Converter Based on Zero-Current Duration Time of Secondary Diode

In order to achieve higher efficiency for the unregulated LLC series resonant converter, the switching frequency must be equal to the resonant frequency. However, since the converter works in open-loop condition, the switching frequency usually deviates from the resonant frequency in real converter. This paper proposed a new control method to track the resonant frequency of the unregulated LLC series resonant converter. Theoretically, the time of zero diode current in secondary is zero when the working frequency is equal or greater than the resonance frequency, and it is changed as the frequency varies when the working frequency is less than the resonance frequency. The proposed control algorithm is based on the time measurement of zero diode current to realize the resonance frequency tracking. A closed-loop digital controller is designed to realize the proposed tracking approach. The simulation and experiments are conducted to verify the proposed tracking approach. The simulation and experimental results show that (1) the switching frequency can be well controlled to track the resonant frequency, and (2) the tracking accuracy can be at least 96%.

승압 초퍼 기능이 내장된 새로운 태양광 발전용 파워컨디셔너의 개발

Abstract - This paper is related to a new solar power conditioner for a built-in step-up chopper function. In the first step-up chopper proposed solar PV power conditioner for mutually connected in series with the input voltage of the bypass diodes are respectively connected to the positive terminal should install the mutual boosting chopper diode connected in series with the boost chopper switching element between the two power supply and at the same time the first and the second was connected to a second diode and a resonance inductor and a snubber capacitor in series with each other. And the common connection point between the bypass diode and the step-up chopper and the step-up chopper diode common connection point of the switching elements of the input voltage was set to the boost inductor for storing energy. In addition, between the step-up chopper and the step-up chopper diode and a switching element of a joint connection point of the first auxiliary diode and the second common connection point of the auxiliary diode was provided, the resonance capacitor. Between the step-up chopper and the step-up chopper diode and a switching element of a joint connection point and the common connection point of the resonance inductor snubber capacitor and connecting the third secondary diode, between two power supply lines is characterized by configuring the DC link capacitor bus lines in parallel. Therefore, it is possible to suppress the switching loss through, DC link bus lines, as well as there could seek miniaturization and weight reduction of the power conditioner itself by using a common capacitor of the non-polar non-polar electrolytic capacitor having a capacitor, the service life of the circuit can be extended and it is possible to greatly reduce the loss can be greatly improve the reliability of the product and the operation of the product itself.Key Words : Step-up chopper, SPWM inverter, Renewable energy in grid-connected, Solar PV power conditioner, High efficiency†Corresponding Author : Dept. of Electrical Engineering, Masan University, KoreaE-mail : kym728@masan.ac.kr*Dept. of Electrical Engineering, Masan University, Korea**NGP Co.,LTD, Korea접수일자 : 2014년 11월 5일수정일자 : 2014년 11월 24일최종완료 : 2014년 11월 25일

Weighted-Efficiency Enhancement Control for a Photovoltaic AC Module Interleaved Flyback Inverter Using a Synchronous Rectifier

In this paper, a weighted-efficiency enhancement control method for an interleaved flyback inverter using a synchronous rectifier is proposed based on photovoltaic ac modules. In this control method, the operation of the synchronous rectifier is classified according to the voltage spike across the main switch. When the voltage spike across main switch is lower than the rating voltage of main switch, the operation of the active clamp circuit is interrupted to reduce the switching loss of the auxiliary switch. At this time, the synchronous rectifier is operated for the zero-voltage switching of main switch. When the voltage spike across main switch is higher than the rating voltage of main switch, the active circuit is activated to reduce the voltage spike. The synchronous rectifier is operated to reduce the conduction loss of the secondary output diode. Thus, the switching loss of the main switch can be reduced in the low power region, and the weighted efficiency can be improved. A theoretical analysis and the design principles of the proposed method are provided. The method is validated through simulation and experimental results.

Asymmetrical Pulse-Width-Modulated Full-Bridge Secondary Dual Resonance DC-DC Converter

A full-bridge secondary dual-resonant DC-DC converter using the asymmetrical pulse-width modulated (APWM) strategy is proposed in this paper. The proposed converter achieves zero-voltage switching for the power switches and zero-current switching for the rectifier diodes in the whole load range without the help of any auxiliary circuit. Given the use of the APWM strategy, a circulating current that exists in a traditional phase-shift full-bridge converter is eliminated. The voltage stress of secondary rectifier diodes in the proposed converter is also clamped to the output voltage. Thus, the existing voltage oscillation of diodes in traditional PSFB converters is eliminated. This paper presents the circuit configuration of the proposed converter and analyzes its operating principle. Experimental results of a 1 kW 385 V/48 V prototype are presented to verify the analysis results of the proposed converter.

Isolated Switch-Mode Current Regulator With Integrated Two Boost LED Drivers

A new isolated switch-mode current regulator is proposed for an LED driving system. The two boost LED drivers are integrated with the dc/dc converter, which results in a simple structure and low component count. The primary side provides an ac voltage source to the secondary side in which one boost inductor, two switches, and diodes comprise two boost drivers. Each secondary switch controls each LED current to be balanced. The voltage stresses of the primary switches are clamped to the input voltage, and those of secondary switches and diodes are clamped to the output voltages. Furthermore, all switches can easily achieve zero-voltage switching by using the transformer magnetizing current without additional auxiliary circuits. The validity of this proposed circuit is confirmed by the experimental results from a 400-V-input and 150-W-output prototype with two 75-W LED strings.

High-Frequency-Link Soft-Switching PWM DC–DC Converter for EV On-Board Battery Chargers

This paper proposes a high-frequency-link soft-switching pulse-width modulated dc-dc converter for electric vehicle (EV) on-board battery chargers. Zero-voltage switching of power switches is achieved from light load to full load. Reverse-recovery losses can be reduced in the secondary side output diodes without using any additional circuit components. Zero-current switching of output diodes is achieved by using the series-resonant circuit in the secondary side. The circulating current in the primary side full-bridge circuit can be changed by the operation modes of the output diode current. As a result, a high efficiency can be achieved for EV on-board battery chargers. The performance of the proposed converter is evaluated throughout experimental results for a 2.0-kW prototype circuit.

A PSR single-stage flyback LED driver with simple line regulation and quasi-resonant operation

A single-stage flyback driving integrated circuit (IC) for light-emitting diodes (LEDs) is proposed. With an average primary-side current estimation and negative feedback networks, the driver operates in the boundary conduction mode (BCM), while the output current can be derived and regulated precisely. By means of a simple external resistor divider, a compensation voltage is produced on the ISEN pin during the turn-on period of the primary MOSFET to improve the line regulation performance. On the other hand, since the delay time between the time that the secondary diode current reaches zero and the turn-on time of the MOSFET can be automatically adjusted, the MOSFET can always turn on at the valley voltage even if the inductance of the primary winding varies with the output power, resulting in quasi-resonant switching for different primary inductances. The driving IC is fabricated in a Dongbu HiTek's 0.35 μm bipolar-CMOS-DMOS process. An 18 W LED driver is finally built and tested. Results show that the driver has an average efficiency larger than 86%, a power factor larger than 0.97, and works under the universal input voltage (85–265 V) with the LED current variation within ±0.5%.

High-Efficiency AC-DC Switch-Mode Power Supply Using FullBridge Converter Circuits

This paper presents a high-efficiency AC-DC switch-mode power supply (SMPS) using the full-bridge converter circuits. The proposed converter utilizes three full-bridge converter circuits: two full-bridge diode converter circuits and one full-bridge MOSFET converter circuit. The two full-bridge converters are utilized at the primary AC input and the secondary DC output, respectively, and the full-bridge MOSFET converter is used to convert a DC voltage to a high-frequency AC voltage that is converted to another DC voltage with the transformer and the secondary full-bridge diode converter, which is simply referred to as the full-bridge DC-DC converter. However the conventional full-bridge converter has a limit in its operating duty ratio in normal operation, because it results in more conduction loss in light load operation. Therefore, the proposed converter resolves the drawbacks of the conventional full-bridge converter using a modified full-bridge circuit with a DC blocking capacitor in the primary. Thus, the proposed converter has improved total efficiency and performance. The operation principle of the proposed converter is described in detail, and a design example of a prototype is shown. The good performance of the proposed converter is demonstrated through experimental results of the implemented prototype based on the design example.

Unveiling the effects of post-deposition treatment with different alkaline elements on the electronic properties of CIGS thin film solar cells

Thin film solar cells with a Cu(In,Ga)Se2 (CIGS) absorber layer achieved efficiencies above 20%. In order to achieve such high performance the absorber layer of the device has to be doped with alkaline material. One possibility to incorporate alkaline material is a post deposition treatment (PDT), where a thin layer of NaF and/or KF is deposited onto the completely grown CIGS layer. In this paper we discuss the effects of PDT with different alkaline elements (Na and K) on the electronic properties of CIGS solar cells. We demonstrate that whereas Na is more effective in increasing the hole concentration in CIGS, K significantly improves the pn-junction quality. The beneficial role of K in improving the PV performance is attributed to reduced recombination at the CdS/CIGS interface, as revealed by temperature dependent J-V measurements, due to a stronger electronically inverted CIGS surface region. Computer simulations with the software SCAPS are used to verify this model. Furthermore, we show that PDT with either KF or NaF has also a distinct influence on other electronic properties of the device such as the position of the N1 signal in admittance spectroscopy and the roll-over of the J-V curve at low temperature. In view of the presented results we conclude that a model based on a secondary diode at the CIGS/Mo interface can best explain these features.

Design and Analysis of LLC Resonant Converter for PV Energy Harvest

Different types of converters are used for photovoltaic energy harvest. But the disadvantages are higher switching losses and they cannot maintain the efficiency for wide input range. In this paper a dual mode resonant converter is proposed. This converter can change the operating modes depending on photovoltaic panel operating condition. This converter achieves zero voltage switching for primary side switches and zero current switching for secondary diodes for both resonant modes. By reducing circulating energy the converter can maintain the high efficiency under wide input range under different output power levels. IndexTerms: Resonant converter, photovoltaic system, zero voltage switching, zero current switching

A Zero-Voltage Switching Full-Bridge DC--DC Converter With Capacitive Output Filter for Plug-In Hybrid Electric Vehicle Battery Charging

In this paper, a novel zero-voltage switching full-bridge converter with trailing edge pulse width modulation and capacitive output filter is presented. The target application for this study is the second stage dc-dc converter in a two stage 1.65 kW on-board charger for a plug-in hybrid electric vehicle. For this application the design objective is to achieve high efficiency and low cost in order to minimize the charger size, charging time, and the amount and the cost of electricity drawn from the utility. A detailed converter operation analysis is presented along with simulation and experimental results. In comparison to a benchmark full-bridge with an LC output filter, the proposed converter reduces the reverse recovery losses in the secondary rectifier diodes, therefore, enabling a converter switching frequency of 100 kHz. Experimental results are presented for a prototype unit converting 400 V from the input dc link to an output voltage range of 200-450 V dc at 1650 W. The prototype achieves a peak efficiency of 95.7%.

동기 정류기를 이용한 태양광 모듈용 플라이백 인버터 소프트 스위칭 제어 기법

In this paper, high efficiency control method for flyback inverter with synchronous rectifier(SR) based on photovoltaic AC modules is proposed. In this control method, the operation of SR is classified according to the voltage spike across main switch SP. When the voltage spike across SP is lower than the rating voltage of SP, the operation of active clamp circuit is interrupted for reducing the switching loss of auxiliary switch. In this time, the SR is operated for soft-switching of SP. When the voltage spike across Sp is higher than the rating voltage of SP, the operation of active circuit is activated for reducing the voltage spike. The SR is operated for reducing the conduction loss of secondary output diode. Thus, a switching loss of the main switch can be reduced in low power region, and weighted-efficiency can be improved. A theoretical analysis and the design principle of the proposed method are provided. And validity is confirmed through simulation and experimental results.

Novel Zero-Current-Switching Current-Fed Half-Bridge Isolated DC/DC Converter for Fuel-Cell-Based Applications

A novel zero-current-switching (ZCS) current-fed half-bridge isolated dc/dc converter has been proposed in this paper. The proposed converter has potential applications such as front-end dc/dc power conversion for fuel cell and photovoltaic inverters, bidirectional converters for fuel cell vehicles, energy storage, etc. This proposed converter provides a simple solution to the switch turn-off voltage spike problem without any additional components or snubber. It leads to reduced size, lower cost, compactness, and higher conversion efficiency. In addition, the proposed converter has reduced peak current through the components (semiconductor devices and transformer) that reduces their volt-ampere rating and size compared to active-clamped zero-voltage-switching (ZVS) current-fed converters. Voltage across the primary switches is naturally clamped without an additional active clamp or snubber circuit. In addition, voltage across the switch is independent of the duty cycle. ZCS of the primary switches, natural commutation of secondary diodes, and zero-current turn-on of secondary switches are achieved. Therefore, switching transition losses are significantly reduced. Steady-state analysis, operation with the proposed novel ZCS concept, and design of the converter are reported. A 200-W laboratory converter prototype has been built. Experimental results as well as simulation results are presented to validate the analysis and design. A comparison with existing active-clamped ZVS current-fed half-bridge converters has been discussed. The effect of device parasitic is investigated and explained by simulation and experimental results.

Soft-Switching Converter With Two Series Half-Bridge Legs to Reduce Voltage Stress of Active Switches

This paper presents a new soft-switching dc/dc converter for high-input-voltage applications. Two half-bridge converters connected in series with interleaved asymmetric pulsewidth modulation (PWM) are adopted to limit the voltage stress of each power switch at one-half of the input dc bus voltage. In each half-bridge converter, two asymmetrical dc/dc circuits with the same active switches are connected in parallel at the output side to share the load current and reduce the current stresses of the secondary windings and rectifier diodes. Since two half-bridge converters are operated with interleaved PWM, the output ripple currents partially cancel each other so that the resultant ripple current at the output side is reduced. Active switches in the proposed circuit can be turned on at zero-voltage switching during the transition interval due to the resonant behavior by the output capacitance of MOSFETs and the leakage inductance of transformers. Experiments based on a laboratory prototype with 960-W rated power are provided to demonstrate the performance of the proposed converter.

Improved Phase-Shift PWM Converter for Larger Sized PDP Slim Sustain Power Module

New phase-shift pulse width modulation (PWM) converters with a wide zero voltage switching (ZVS) range for the slim sustain power module of over 63-in plasma display panel (PDP) are proposed in this paper. Each proposed converter is composed of two symmetric half-bridge converters (TSHBCs) that are placed in parallel on the primary side and are driven in a phase shifting manner. Two power transformers are connected in series on the secondary side. All the switches in the proposed converters can be turned on with ZVS under all load conditions, while the conduction loss caused by the assistant current source extending the ZVS range can be minimized. Moreover, because the turns ratio of the transformers can be designed to be better than that of the counterparts, the voltage stress across the secondary rectifier diode and the primary conduction loss can be reduced. A low-profile design is also achieved due to the use of the two small-sized transformers, which results in a slim power supply. In this paper, the circuit configurations, operation principle, relevant analysis results, and design example of the proposed converters are presented. Experimental results demonstrate that the proposed converters can achieve a significant improvement in the efficiency for a prototype converter realized with the specification of 80-in PDP sustain power module (320-385 Vdc input, 205 Vdc/5 A output).

High-Step-Up and High-Efficiency Fuel-Cell Power-Generation System With Active-Clamp Flyback–Forward Converter

A high-efficiency fuel-cell power-generation system with an active-clamp flyback-forward converter is presented in this paper to boost a 12-V dc voltage into a 220-V 50-Hz ac voltage. The proposed system includes a high-efficiency high-step-up interleaved soft-switching flyback-forward converter and a full-bridge inverter. The front-end active-clamp flyback-forward converter has the advantages of zero-voltage-switching performance for all the primary switches, reverse-recovery-problem alleviation for the secondary output diodes, large voltage-conversion ratio, and small input-current ripple. Furthermore, there are two coupled inductors in the proposed converter. Each coupled inductor can work in the flyback mode when the corresponding main switch is in the turn-on state and in the forward mode when it is in the turnoff state, which takes full use of the magnetic core and improves the power density. In addition, the full-bridge inverter with an LC low-pass filter is adopted to provide low-total-harmonic-distortion ac voltage to the load. Therefore, high-efficiency and high-power-density conversion can be achieved in a wide input-voltage range by employing the proposed system. Finally, a 500-W prototype and another 1-kW converter are implemented and tested to verify the effectiveness of the proposed system.

A Novel Adaptive Synchronous Rectification System for Low Output Voltage Isolated Converters

The design of efficient isolated low output voltage converters is a major concern due to their widespread use. One of the preferred methods used to maximize their efficiency is synchronous rectification (SR), i.e., the replacement of the secondary side diodes with MOSFETs to decrease conduction losses. However, depending on the topology being used, SR might not provide the required efficiency improvement or even be easily implemented. This paper presents a novel SR system that can be applied to converters with symmetrically driven transformers and to converters from the flyback family; in both cases, the proposed system adaptively generates a control signal that controls a synchronous rectifier MOSFET placed in parallel with each diode, turning it on during the conduction intervals of the diodes. The proposed system uses only information from the secondary side, thus avoiding breaking the isolation barrier; it can be built using a few low-cost analog components, is reliable and simple, and could be easily implemented in an integrated circuit. Up to a 3% improvement is demonstrated in a 3.3–5-V 120-W push–pull converter, and up to a 2.5% improvement is obtained in a 5-V 50-W flyback converter, with both of them designed for telecom applications.

An Improved Current-Fed ZVS Isolated Boost Converter for Fuel Cell Applications

This paper proposes an improved current-fed zero-voltage switching isolated boost converter suitable for fuel cell applications. Preserving the inherent advantages of the current-fed converter which include smaller input current ripple, lower diode voltage rating, and lower transformer turns ratio, the proposed converter does not require any clamping and start-up circuits unlike the conventional current-fed converters. The voltage ratings of the primary switches and secondary diodes of the proposed converter are significantly reduced. Some alternative schemes of the proposed converter without the voltage-second unbalance are presented. These characteristics of the proposed converter lead to a high overall efficiency over wider load range. Experimental results on a 1 kW prototype are provided to validate the proposed concept.

Influence of Shockley Stacking Fault Generation on Electrical Behavior of 4H-SiC 10 kV MPS Diodes

The influence of stacking fault (SF) generation on the reverse blocking characteristics has been investigated on SiC 10 kV, 5 A Merged PiN (MPS) diodes. For the first time, we have observed that the generation of SFs under forward biased stress increases the reverse leakage current. In addition, the presence of a secondary diode formed by the electrical stress was observed and attributed to the breakdown voltage failure on certain devices.

두 개의 변압기를 이용한 전류불균형 개선 하프브리지 LLC 공진형 컨버터

본 논문은 상이한 누설인덕턴스를 가진 두 개의 변압기를 이용하여 전류불균형을 개선한 하프브리지 LLC 공진형 컨버터를 제안한다. 제안된 컨버터는 변압기의 누설인덕턴스와 자화인덕턴스 및 공진커패시턴스를 이용하여 공진하고, 넓은 부하영역을 가지며, 경부하에서도 영전압스위칭 조건을 만족한다. 직/병렬로 연결된 두 개의 변압기는 동작모드에 따라 변압기 또는 공진인덕턴스로써 교대로 동작하고, 변압기 2차측에는 누설인덕턴스를 이용하므로 별도의 출력 필터인덕턴스가 필요하지 않다. 또한 제안된 컨버터는 두 변압기의 상이한 누설인덕턴스와 하프브리지 스위치의 비대칭 펄스폭변조를 이용하여 2차측 정류다이오드의 전류불균형 문제를 개선한다. 본 논문에서는 제안된 컨버터의 동작원리를 모드별로 설명하고 프로토타입 컨버터의 설계 예를 제시한다. 제안된 컨버터의 우수한 성능을 입증하기 위하여 설계된 프로토타입의 회로파라미터로써 프로토타입 컨버터를 제작하고 실험하였다. 제안된 컨버터의 우수한 성능을 실험결과를 통하여 보인다. This paper presents current unbalance improved half-bridge LLC resonant converter using the two transformers with different leakage inductances. The proposed converter resonates with the leakage inductance and magnetizing inductance of the transformer and the resonant capacitance. The converter operates in a wide load range and satisfies the zero voltage switching even under the light load. The series-parallel connected two transformers act as the transformers or the resonant inductances according to the operational modes, and the separate output filter inductance in the transformer secondary is not needed using the leakage inductance. The current unbalance of the secondary diode rectifier is improved using the different leakage inductances of the two transformers and the asymmetrical pulse-width modulation (PWM). In this paper, the operational principle of the converter is explained by the modes, and the design example for the prototype is also shown. To validate the performance of the converter, the prototype is implemented as the designed circuit parameters and the good performance of the proposed converter is shown through the experimental results