Single-Stage Single-Switch Four-Output Resonant LED Driver with High Power Factor  and Passive Current Balancing

 

Abstract

A resonant single-stage single-switch four-output  LED driver with high power factor and passive current balancing is proposed. By controlling one output current, the other output currents of four-output LED driver can be controlled via passive current balancing, which makes its control simple. When magnetizing inductor current operates in critical conduction mode (CRM), unity power factor is achieved. The proposed LED driver uses only one active switch and one magnetic component, thus it benefits from low cost, small volume and light weight. Moreover, high efficiency performance is achieved due to single-stage power conversion and soft switching characteristics. The characteristics of the proposed LED driver are studied in this paper and experimental results of two 110W four-output isolated LED drivers are provided to verify the studied results.

PROPOSED SYSTEM:

In this paper, a resonant single-stage single-switch four-output LED driver with power factor correction and passive current balancing is proposed and analyzed. It combines with a single-switch secondary side resonant PFC converter and passive current balancing circuit composed of resonant capacitors. When magnetizing inductor current operates in critical conduction mode (CRM), unity power factor can be achieved and not affected by the resonant current. By control output current of one output, the other output currents of the proposed LED driver can be controlled via passive current balancing, which makes the control simple. Furthermore, the proposed LED driver is a single-stage single-switch converter. It uses only one active switch and one magnetic component. Comparing with conventional two-stage multi-output converters, the proposed LED driver benefits with low cost, small size, high efficiency and light weight. Experimental results of two 110W four-output LED drivers are provided to verify the studied results.

 

EXISTING  SYSTEM:

In terms of circuit and control complexity, the passive current balancing techniques are generally simple, as they only require one driving circuit and uses passive components to achieve current balancing, a current balancing method composed of LCL-T resonant rectifiers is proposed. A capacitor-isolated multiple-string LED driver with daisy-chained transformers is proposed. However, above passive current balancing methods need more inductors or transformers. In contrast, the current balancing method based on capacitor charge-balancing scheme has the advantages of high power density and cost effectiveness. However, the existing capacitance current balancing circuits are all designed based on half-bridge dc input power converters and need more transformer windings. It makes these LED drivers complex. Furthermore, IEC61000-3-2 Class C for lighting equipment establishes a strict requirement for input current harmonic content of power converter. Power factor correction (PFC) should be used in LED driver to provide sinusoidal input current in high power application. Therefore, the solution can only be used as a second power stage in LED driver. Pre-stage with power factor correction must be used. Moreover, the two-stage power conversion with PFC pre-regulator and dc-to-dc converters suffers from lower efficiency and higher volume and cost. Single-stage LED driver has been studied in recently years. a single-stage multi-output asymmetrical half-bridge PFC converter is proposed. But it needs more inductors and switches. a single-stage dual-output buck-boost PFC converter is proposed. Although the efficiency is improved due to single-stage power conversion and use only one inductor, it needs more active switches and the control is complex.

 

CONCLUSION

A single-stage single-switch four-output resonant LED  driver is proposed. Current balanced a four outputs can be achieved by only controlling one output current. Single-stage power factor correction and four constant current outputs are achieved together by using only one active switch and one magnetic component. Compared with conventional two-stage multiple output converters, the proposed LED driver benefits from significant overall cost saving, small size and light weight of device. Experimental results are presented to verify the proposed LED driver, and demonstrate the advantages. This solution can be easily applied to high power LED lighting such as panel lighting. Although only four constant current outputs solution is discussed in this paper, the proposed LED driver can be easily extended to realize multiple constant outputs to fulfill different system requirements.

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