Self-driven Synchronous Rectification Research Articles

LCD 모듈 검사장비용 LED 백라이트 드라이브 시스템을 위한 고효율 반브리지 직류-직류 전력변환기

This paper presents a high efficiency half-bridge DC-DC converter for an LED backlight drive system of LCD module inspection equipment. The proposed converter improves the converter efficiency using characteristics of the asymmetrical half-bridge converter and the self-driven synchronous rectifier, and thus improves the total efficiency of the LED backlight drive system. The synchronous rectifier applied to the proposed converter is the new topological synchronous rectifier, which changes slightly the transformer structure and the synchronous switch connection in the asymmetrical half-bridge converter with a conventional self-driven synchronous rectifier. Since the proposed converter utilizes the transformer leakage inductor as its resonant inductor, its structure is simplified. The proposed converter well operates under the universal DC input voltage (<TEX>$250{\sim}380V$</TEX>). The operational principle and a design example for a 100W prototype are discussed in detail, respectively. Experimental results are shown for the designed prototype converter under universal DC input voltage.

High efficiency asymmetrical half-bridge converter using a self-driven synchronous rectifier

A novel high efficiency asymmetrical half-bridge converter using a self-driven synchronous rectifier is presented. The proposed converter improves the system efficiency using the characteristics of the asymmetrical half-bridge converter and the self-driven synchronous rectifier. The synchronous rectifier applied to the proposed converter is the new topological synchronous rectifier, which is a slightly modified type of the conventional synchronous rectifier used in the conventional asymmetrical half-bridge converter. The type of the new topological synchronous rectifier slightly changes the transformer structure and the synchronous switch connection in the asymmetrical half-bridge converter with a conventional self-driven synchronous rectifier. The operational principle of the proposed converter is explained in detail. Since the proposed converter utilises the transformer leakage inductor as its resonant inductor, its structure is simplified. A design example for a 90 W (12 V/7.5 A) prototype is discussed in detail. Experimental results are shown for the designed prototype converter under universal AC input voltage (180–265 V). It is shown that the efficiency of the proposed converter can be significantly improved.

A Novel Non-Isolated Full Bridge Topology for VRM Applications

In this paper, a new non-isolated full bridge (NFB) topology is introduced to solve the narrow duty cycle and hard switching problems of the buck converter in low output voltage, high output current applications. In comparison to the Buck converter, it operates at a significantly wider duty cycle and can achieve zero voltage switching for the high side MOSFETs. The NFB significantly reduces the input peak current and transfers a portion of the primary side energy directly to the load thereby reducing the stress on the synchronous rectifiers and filter inductors. Using self-driven synchronous rectifiers, the body diode conduction loss is reduced since no dead time is required between the primary side MOSFETs and the synchronous rectifiers. Given these significant advantages, the NFB can achieve higher efficiency than a two and three phase interleaved buck at the same power level. The efficiency gain enables the NFB to operate at a high switching frequency thereby enabling smaller output inductors to be used to achieve improved dynamic performance. Experimental results and analysis demonstrate that the new NFB can significantly improve the performance of a voltage regulator. The prototype built operated at 500 kHz, 12 V input, 1 V output, up to 30 A load and achieved an efficiency of 84.4% at 30 A load. A 1 MHz prototype achieved a full load efficiency of 82.1%. In comparison, the efficiency of a two and three phase Buck prototype was 79.7% and 82.6% at 30 A load and at 500kHz switching frequency.

Self-Driven Synchronous Rectification Scheme Without Undesired Gate-Voltage Discharge for DC-DC Converters With Symmetrically Driven Transformers

This paper proposes a new self-driven synchronous rectification scheme for dc-dc converters with symmetrically driven transformers and wide input voltage range. The driving signals are obtained from the output inductor. Two auxiliary switches are utilized to turn off the main switches properly. Two extra auxiliary switches, which are controlled by a delayed signal from the inductor, are added to avoid the undesired gate discharge. This approach can achieve high efficiency and is suitable for practical applications. Experimental results based on a 36-75 V input, 2.5 V/30 A output prototype are shown to verify the proposed scheme.

Current-Fed Dual-Bridge DC–DC Converter

A new isolated current-fed pulsewidth modulation dc-dc converter-current-fed dual-bridge dc-dc converter-with small inductance and no deadtime operation is presented and analyzed. The new topology has more than 3times smaller inductance than that of current-fed full-bridge converter, thus having faster transient response speed. Other characteristics include simple self-driven synchronous rectification, simple housekeeping power supply, and smaller output filter capacitance. Detailed analysis shows the proposed converter can have either lower voltage stress on all primary side power switches or soft switching properties when different driving schemes are applied. A 48-V/125-W prototype dc-dc converter with dual output has been tested for the verification of the principles. Both simulations and experiments verify the feasibility and advantages of the new topology

DC–DC Converter Using a Multiple-Coupled Inductor for Low Output Voltages

A new multiple-coupled inductor (MCI) is proposed for good cross regulation among low output voltages, high power density, and reduced converter volume. Moreover, a current doubler rectifier and a self-driven synchronous rectifier are presented to achieve high efficiency. The structure of the MCI is composed of four windings on a common core, and has the properties of a current doubler and good cross regulation. A dc-dc half-bridge converter using the proposed MCI is analyzed and designed for 40-W low output voltages (3.3, 4.5 V). This converter is very suitable for high current and low voltage applications. It is shown via experimental results that efficiency of over 90% and cross regulation of about 5% are achieved

A novel ZCZVT forward converter with synchronous rectification

A novel zero-current-zero-voltage transition (ZCZVT) forward converter with synchronous rectification (SR) is presented in this paper. The proposed converter is operating at 300 kHz and processes the features of both zero-voltage transition (ZVT) at turn on and zero-current transition (ZCT) at turn off for the main switch. The auxiliary switch also achieves zero-current switching (ZCS). The flux of transformer can be reset without tertiary winding. The steady-state analysis and design considerations are investigated in detail in this work. Moreover, a self-driven synchronous rectification is also added to the ZCZVT forward converter to reduce the conduction losses of the output rectifier. For 48-V input and 12-V 100-W output, a prototype of the proposed converter for 300-kHz switching is built to verify the theoretical analysis. Finally, the power losses are well estimated. The overall efficiency of the proposed converter is achieved at 89% at full load.

A Novel Driving Scheme for Synchronous Rectifier Suitable for Modules in Parallel

In this paper, a short circuit phenomenon when dc-dc modules with self-driven synchronous rectifier (SR) run in parallel is described. Three existing driving schemes are analyzed and compared. A novel driving scheme for SR maintains the performance of SR as a self-driven scheme, while solving the problem of a short circuit when modules run in parallel. In addition, the amplitude of an SR driving voltage can be adjusted by using the proposed scheme. Therefore, the scheme is more attractive in the applications of comparatively high-voltage output. The principle of operation and the characteristics of the scheme are analyzed and verified on a 36-75V input 1.8-V/60-A output experimental prototype, whose size is 1/4 brick and efficiency is above 90% under rating conditions.

New Self-Driven Synchronous Rectification System for Converters With a Symmetrically Driven Transformer

Synchronous rectification (SR) is mandatory to achieve good efficiencies with low output voltages. If the transformer is driven asymmetrically without dead times, self-driven SR (SDSR) is a very interesting solution. However, if the transformer is driven symmetrically, the synchronous rectifiers are off during the dead times and, as a consequence, the efficiency is lowered. This paper deals with a new SDSR system that keeps the rectifiers on even during the dead times. Thus, it can be used to obtain very low output voltages, such as 1.5 V, with quite good efficiency. Moreover, it can be used over a wide input voltage range. The new system is implemented in a prototype in order to measure the real efficiency that can be achieved with the proposed scheme.

Effect of Resonant Transition on Efficiency of Forward Converter With Active Clamp and Self-Driven SRs

Forward converter with active clamp is a suitable topology for a low output voltage and high output current dc-dc power supply module. The topology can be used in a resonant transition manner to obtain a low voltage over the main switch at turn-on instant. A low voltage can be obtained by adjusting the magnitude of the magnetizing current of the transformer and the delay between the two primary side switches. An increased magnetizing current, however, increases conduction losses in the primary side of the converter and may consume the advantage gained in the switching losses. The converter can also be easily used for self-driven synchronous rectification. However, pursue for low switching losses for the primary side switch may deteriorate performance of the self-driven synchronous rectifiers, particularly at high loads. This paper presents a study of the applicability and advantage of the use of the resonant transition in Forward with active clamp and self-driven synchronous rectifiers. The emphasis is on the comparison of the achieved efficiency with different voltage levels over the primary switch prior to turning on. Measurement results show that, at low loads, a reduced voltage level improves the efficiency but, on the other hand, at high loads the advantage is not so significant, or it may be totally lost, mainly due to the increased losses of the self-driven synchronous rectifiers. The paper includes discussion on the effect of the magnetizing inductance on the efficiency of the converter and the optimal voltage level at which the primary switch should be turned on. Measurement results from a 3.4-V 30-A prototype converter are included.

Dual-Bridge DC–DC Converter: A New Topology Characterized With No Deadtime Operation

Two new topologies characterized by no deadtime and small valued filter inductor, the Dual-Bridge dc-dc converter and the Dual-Bridge dc-dc converter with ZVS, are presented and analyzed. Compared to the conventional Full-Bridge converter, the dc-dc converters with the proposed topologies have lower input current ripple, less stress on power switching components and smaller output filter inductor. Simple self-driven synchronous rectification can be used in the new topologies for high efficiency implementation. Prototype dc-dc converters have been tested for the verification of the principles. Both simulations and experiments verify the feasibility and advantages of the new topologies. The advantages and disadvantages of the topologies are discussed.

Single-stage ac-to-dc converter with self-driven synchronous rectification that complies with en61000-3-2 regulations

When low output voltage and EN61000-3-2 compliance are put together, not too many options can be used, especially if the power range is between 300-600 W. This paper presents one of the best solutions to comply with both specifications at the same time: the use of a single-stage topology to comply with the low-frequency harmonic limits combined with a half-bridge converter with complementary control, which is a very good option to obtain low output voltages with high efficiency.

Low output voltage AC/DC converter with a new scheme of synchronous rectification that complies with IEC 1000-3-2 regulations

The aim of this paper is to study the performance of an AC/DC converter with low output voltage and low input current harmonic content. In order to obtain low output voltages with a high efficiency, synchronous rectification is mandatory. When the output voltage is low, it is very difficult to use self-driven synchronous rectification and additional windings are used to properly drive the metal oxide semiconductor field effect transmitters (MOSFETs). Besides this, IEC 1000-3-2 regulations impose low input current harmonic contents for power levels higher than 75 W. In this paper, a recently proposed synchronous rectification scheme is combined with a modified input current shaper to design a 100 W, 3.3 V AC/DC converter that complies with IEC 1000-3-2 regulations. The efficiency obtained in the prototype was very high for this application (86%) and both the size increase and the cost increase were quite low in comparison with the original topology with no synchronous rectification and no IEC 1000-3-2 compliance.

A new driving scheme for synchronous rectifiers: single winding self-driven synchronous rectification

Single winding self-driven synchronous rectification (SWSDSR) approach is a new driving circuit that overcomes the limitations of the traditional driving schemes, becoming an interesting alternative to supply new electronic loads such as microprocessors. Traditional self-driven synchronous rectification (SDSR) technique has shown very good performance to improve efficiency and thermal management in low-voltage low-power DC/DC converters, however it can not be extended to the new fast dynamic, very low voltage applications. SWSDSR scheme is based on an additional winding in the power transformer (auxiliary winding). It allows for maintaining the synchronous rectifiers (SRs,) on even when the voltage in the transformer is zero, which is impossible to do in traditional self-driven approaches. It also makes it possible to drive properly the SRs even in very low voltage applications, 1.5 V or less. Coupling of the windings strongly affects the performance of the SWSDSR technique. The influence of the coupling between the different windings is analyzed through simulations of different transformers designed for the same application. Models of transformers are generated with a finite element analysis (FEA) tool. Goodness of the SWSDSR scheme is validated through experimental results.

Trends in low power low voltage d.c./d.c. converters

New integrated circuits are demanding very low supply voltages (1.5 V, 1.2 V, ...) with a very high quality. Low supply voltages allow for reducing the power consumption and increasing the integration density as well as the operation speed of the integrated circuits. Powering properly these new electronics loads is not a trivial question at all. New dynamic response specifications affect dramatically the design of the power supply. Topology selection does not depend only on size and efficiency considerations but also on its dynamic response.Size, efficiency and dynamic response are strongly related (Fig. 1). Critical issues in the design of low voltage power sup-plies are the topology selection, switching frequency, efficiency, dynamic response, packaging, input voltage, transformer design, etc. Design of these new power supplies is very complex, and all these aspects should be considered together Design of the transformer becomes very critical when auxiliary windings are needed to drive the Synchronous Rectifiers. Modern technologies are necessary to couple properly all the windings.Topologies used in the last years to supply low voltage circuits (forward with active clamp, half bridge with complementary control) are not the best option now, because their dynamic response is not good enough to supply properly the new loads.Topologies that drive symmetrically the transformer (classical half bridge, push pull) are a better option, but new techniques to implement self-driven synchronous rectification are necessary. Two possible solutions for powering the new IC are analyzed in this paper, and validated with experimental results.

Design of high efficiency interleaved active clamp zero voltage switching forward converter

A high efficiency interleaved active clamp forward converter with self-driven synchronous rectifiers for a modular power processor is presented. To simplify the gate drive circuits, the n–p MOSFETs coupled active clamp method is used. An efficiency of about 90% for a load range of 50-100% is achieved. Details of design for the power stage and current mode control circuit are provided, and also some experimental results are given.

New fabrication method for planar multilayer windings used in low-profile magnetic components

A new design and fabrication method for planar windings with multilayers is presented. This method can virtually eliminate external soldering or conductive vias, thus reducing dc resistance and increasing reliability. Compared to the previously reported folding methods for winding fabrication, this method maximizes the use of the window height and minimizes the waste of copper area in manufacturing. The winding pattern is cut using a computer numerically controlled machine, or the punching/pressing process, which is cleaner than the commonly used etching process. The whole winding assembly is completed by a folding process. The primary and secondary windings in a transformer can be interleaved, resulting in low leakage inductance. Practical examples of low-profile transformers and inductors were constructed and tested in an active-clamped forward dc-dc converter with self-driven synchronous rectifiers. Experimental results are presented to show that such transformers/inductors are particularly useful for the design of low-profile and high power density converter modules.

Evaluation of synchronous-rectification efficiency improvement limits in forward converters

Design trade-offs for different implementations of the forward power converter with synchronous rectifiers are presented, and effects of the synchronous rectifier driving method on the conversion efficiency are evaluated. Specifically, the merits and limitations of the RCD-clamp and active-clamp reset approaches for a power converter with self-driven synchronous rectifiers are discussed. Estimates of the upper limits of the efficiency improvements of the discussed synchronous rectification approaches relative to the Schottky diode implementation are derived. Finally, experimental comparisons of efficiencies for an offline, 3.3 V/20 A forward power converter power stage are presented and compared with the theoretically estimated ones.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>