Yilei Gu

Three-level LLC series resonant DC/DC converter

Paper presents a three level soft switching LLC series resonant DC/DC converter. ZVS is achieved for each main switch without any auxiliary circuit. Voltage stress of each main switch is half of input voltage. ZCS is achieved for rectifier diodes. Wide input/output range can be achieved under low frequency range because of two-stage resonance. Only one magnetic component is needed in this converter. Efficiency is higher in high line input, so this converter is fit for power products with hold up time requirement. The principle of operation and the characteristics of the new converter are analyzed and verified on a 500 V/spl sim/700 V input 54 V/10 A output experimental prototype, whose efficiency is 94.1% at rating condition.

Three level LLC series resonant DC/DC converter

Paper presents a three level soft switching LLC series resonant DC/DC converter. ZVS is achieved for each main switch without any auxiliary circuit. Voltage stress of each main switch is half of input voltage. ZCS is achieved for rectifier diodes. Wide input/output range can be achieved under low frequency range because of two-stage resonance. Only one magnetic component is needed in this converter. Efficiency is higher in high line input, so this converter is fit for power products with hold up time requirement. The principle of operation and the characteristics of the new converter are analyzed and verified on a 500 V/spl sim/700 V input 54 V/10 A output experimental prototype, whose efficiency is 94.1% at rating condition.

A novel ZVS resonant reset dual switch forward DC/DC converter

Paper presents a new topology named ZVS resonant reset dual switch forward DC/DC converter, which, compared with resonant reset single switch forward DC/DC converter, maintains the advantage that duty cycle can be more than 50%, at the same time disadvantages of high voltage stress for main switches and low efficiency are overcome. In addition, soft switching is achieved for all switches of the presented topology. Therefore, this proposed topology is very attractive for high input, wide range and high efficiency applications. In this paper, the operation principle and characteristic of this topology are analyzed in detail. Finally, the advantages mentioned above are verified by experimental result.

A simple structure of LLC resonant DC-DC converter for multi-output applications

Multi-output LLC resonant topologies with asymmetrical structures dedicating to multi-output power supply systems, having limitation of lowest load, are presented in this paper. According to output power level, different configuration of secondary output end can be flexibly adapted. Consequently, the presented topology is a favorable candidate for such application as whose outputs are not symmetrical, i.e. compared with auxiliary output, power level of main output is comparatively higher. In addition, all switches of the very topology operate under the condition of ZVS and therefore it is applicable to such occasion as high frequency, high power density. Asymmetrical operating principle and ZVS operation are analyzed in detail, moreover key parameter design considerations are presented. Finally, the analysis above is verified both by simulation and experiment.

Voltage doubler application in isolated resonant converters

Two basic conditions of voltage-doubler adopted in isolated DC/DC converter are analyzed. According to the basic conditions, that voltage-doubler can be both adopted in LC series resonant converter and LLC multi-resonant converter. Operation characteristic of voltage-doubler adopted in isolated DC/DC converter is described in detail based on the analysis of voltage-doubler rectifying LLC multi-resonant converter. Advantages of voltage-doubler rectifying LLC multi-resonant converter are described in detail as follows, structure of transformer, in which one winding is involved on its secondary side, is simple, voltage stress of output capacitor is half of output and extra voltage balancing circuit is excluded. Two rectifier diodes are included on output end, voltage and current stress of diodes respectively equal output voltage and current. Therefore, the topology is a preferable candidate for such application as low-medium power level DC/DC converter with high output voltage. In addition, principle of automatic voltage balancing for output capacitor is presented, moreover design of key parameter is specified as well. Presented characteristics of the very topology are verified by a prototype, whose output is 500 V and efficiency of full load reaches 92.3%.

A Novel Three Level Full Bridge Resonant Dc-Dc Converter Suitable for High Power Wide Range Input Applications

To make downstream dc-dc converters compatible with both single and three phases PFC stages for system integration, a novel three-level full bridge resonant dc-dc converter was proposed. This converter combines the LLC topology, which maintains merits as ZVS for all primary side main switches and ZCS for secondary side diodes under wide range inputs, and the three-level technique, which is suitable for high voltage input applications, together. In addition, full bridge configuration endows the high power capability to the proposed converter. The detail operation principles, as well as the design considerations and loss calculation, were presented. The validity and applicability were also verified by a 1kW prototype, while the maximum efficiency reaches 96.2%. Therefore, the proposed converter is very attractive for the system integration applications which have requirement to be compatible with 400V and 800V PFC systems, while high power capability must be taken into account. Consequently, it is of practical significance for industry to simplify power supplys variety and lower cost.

A Flexible Converter With Two Selectable Topologies

In order to satisfy the requirement of wide adaptability for standard power modules in the scheme of power electronics system integration, a novel conception of flexible converter is proposed. Next, a practical case of flexible converter with two selectable topologies based on LLC resonant converter with frequency modulation is also proposed. This converter can operate under two various topologies to satisfy various applications only by altering the connecting mode of the output pins. This converter is suitable for two applications of V/I output and 2V/(I/2) output and the voltage stresses and current stresses of all main components are peer to peer under these two applications. The design considerations of small-signal, electromagnetic compatibility, and layout for the flexible converter are also discussed. A prototype with selectable output of 110 V/10 A and 220 V/5 A is built to verify the aforementioned analysis and the highest efficiency is above 96%.

Research on control type soft switching converters

Paper clarifies the definition of control type soft switching and presents five characteristics for control type soft switching topologies. The theory of five characteristics is verified in the existing control type soft switching topologies, and a series of new control type soft switching topologies, such as buck, boost, buck-boost, cuk, zeta, sepic, flyback, and forward are constructed. A 200 kHz prototype of 48 V input, 19 V output, whose highest conversion efficiency is 96.1% is built to verify the theory of five characteristics for control type soft switching.

Wide Range Dual Switch Forward-Flyback Converter with Symmetrical RCD Clamp

This paper proposes a wide range dual switch forward-flyback with current-doubler rectifier (CDR) converter which adopts staggered clamp structure with two symmetrical RCD type circuit. It overcomes the shortcoming that duty ratio cannot be more than 50% of conventional dual switch forward converters. Compared with the conventional single switch active-clamp forward-flyback converter with CDR, it maintains the advantages of wide voltage input and high efficiency, moreover, reduces the voltage stress of main switch to half of the former in a relative low cost and simple structure. The improved symmetrical RCD clamp structure are also recommended to be used in dual switch forward converter for high and wide range voltage input application, which is a kind of slight dissipative type clamp circuit for it enhances the magnetic reset efficiency greatly compared with conventional RCD clamp circuit. The principle of operation and characteristics of the novel converter are verified on a 200 V-400 V input and 9.5 V/15 A output experimental prototype

A Novel LLC Resonant Converter Topology: Voltage Stresses of All Components in Secondary Side Being Half of Output Voltage

Paper presents a novel LLC resonant converter topology, where voltage stresses of all components in secondary side are half of output voltage. The advantages, which are featured in conventional LLC converter, i.e. being easy to obtain full range ZVS for primary side switches, being easy to obtain ZCS for secondary side diodes, resonant inductors and transformer being easy to be integrated and wide range application, are taken on in the presented topology as well, furthermore the prominent advantages that voltage stresses of secondary side diodes and secondary side capacitors are half of output voltages are taken on. Therefore this converter is fit for application with the characteristic of high output voltage. Evolvement of this topology, detailed operation principle and design considerations of key parameters are detailed analyzed. Finally, an experimental prototype of 1100 W is built to verify the reliability and practicability of the proposed topology. Efficiency of the prototype with full load is above 96%