A novel control scheme of quasi resonant valley-switching for high-power-factor ac-to-dc led drivers

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A NOVEL CONTROL SCHEME OF QUASI-RESONANT VALLEY-SWITCHING FOR
HIGH-POWER-FACTOR AC-TO-DC LED DRIVERS
By
A
PROJECT REPORT
Submitted to the Department of electronics & communication Engineering in the
FACULTY OF ENGINEERING & TECHNOLOGY
In partial fulfillment of the requirements for the award of the degree
Of
MASTER OF TECHNOLOGY
IN
ELECTRONICS & COMMUNICATION ENGINEERING
APRIL 2016

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CERTIFICATE
Certified that this project report titled “A NOVEL CONTROL SCHEME OF QUASI-
RESONANT VALLEY-SWITCHING FOR HIGH-POWER-FACTOR AC-TO-DC LED
DRIVERS” is the bonafide work of Mr. _____________Who carried out the research under my
supervision Certified further, that to the best of my knowledge the work reported herein does not
form part of any other project report or dissertation on the basis of which a degree or award was
conferred on an earlier occasion on this or any other candidate.
Signature of the Guide Signature of the H.O.D
Name Name

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DECLARATION
I hereby declare that the project work entitled “A NOVEL CONTROL SCHEME OF QUASI-
DRIVERS” Submitted to BHARATHIDASAN UNIVERSITY in partial fulfillment of the
requirement for the award of the Degree of MASTER OF APPLIED ELECTRONICS is a record
of original work done by me the guidance of Prof.A.Vinayagam M.Sc., M.Phil., M.E., to the
best of my knowledge, the work reported here is not a part of any other thesis or work on the
basis of which a degree or award was conferred on an earlier occasion to me or any other
candidate.
(Student Name)
(Reg.No)
Place:
Date:

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ACKNOWLEDGEMENT
I am extremely glad to present my project “A NOVEL CONTROL SCHEME OF QUASI-
DRIVERS” which is a part of my curriculum of third semester Master of Science in Computer
science. I take this opportunity to express my sincere gratitude to those who helped me in
bringing out this project work.
I would like to express my Director, Dr. K. ANANDAN, M.A.(Eco.), M.Ed., M.Phil.,(Edn.),
PGDCA., CGT., M.A.(Psy.) of who had given me an opportunity to undertake this project.
I am highly indebted to Co-Ordinator Prof. Muniappan Department of Physics and thank from
my deep heart for her valuable comments I received through my project.
I wish to express my deep sense of gratitude to my guide
Prof. A.Vinayagam M.Sc., M.Phil., M.E., for her immense help and encouragement for
successful completion of this project.
I also express my sincere thanks to the all the staff members of Computer science for their kind
advice.
And last, but not the least, I express my deep gratitude to my parents and friends for their
encouragement and support throughout the project.

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ABSTRACT:
This paper presents a novel control scheme of quasi-resonant (QR) mode and valley-
switching for high-power-factor (PF) ac-to-dc light-emitting diode (LED) drivers. The proposed
driver control scheme is based on a buck PF corrector converter, which is operated in QR valley-
switching. The proposed control scheme can directly sense the QR valley signal from the current
sensor, and it is definitely different from the conventional method which senses the QR valley
signal from auxiliary winding. The cost and size of the driver circuit can be remarkably reduced
when the proposed control scheme is adopted. Furthermore, the proposed circuit can provide not
only high PF and low total harmonic distortion but also high conversion efficiency. Up to 0.99
PF and 91.5% efficiency are obtained from an 8-W (40-W replaced) LED bulb driver prototype.

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INTRODUCTION:
In general, the driver circuit design dominates the energy efficiency as significantly as the
light sources. In other words, the lighting product efficiency can be considerably improved via an
appropriate driver circuit. Moreover, acquiring electrical energy from the wall plugs (ac line
voltage source) is the familiar way.
However, LEDs are more suitable to be driven by a dc voltage in accordance with their
characteristics, and thus, an ac-to-dc conversion stage is necessary. Furthermore, the switching
converter is one of the most common and efficient LED driving solutions. In general,
conventional ac-to-dc switching converters are constructed from a diode-bridge rectifier
followed by a bulk capacitor and a dc-to-dc switching converter.
This topology has inherent drawbacks, such as the poor performances in power factor
(PF) and total harmonic distortion (THD). Therefore, an additional PF correction (PFC) stage is
associated with the traditional converter, in order to comply with the current harmonic
regulations and improve the PF at the same time. In spite of its good performance, the two stage
solutions are usually more inefficient and have a lower cost/performance ratio.
However, the conventional control scheme of QR valleyswitching senses the valley
signal from an auxiliary winding, which hinders the magnetic core selection and further raises
the driver cost and size.According, it can be observed that the conventional solution needs not
only an auxiliary winding but also an extra sensing pin on the control integrated circuit (IC), and
thus, the IC package, size, and cost are also limited.
In order to further simplify the bill of material cost and size of the LED driver circuit, this
paper proposes a novel control scheme of QR valley-switching for a high-PF ac-to-dc LED
driver circuit, .

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The proposed control circuit can innovatively sense the QR valley signal from the current
sense, and it is definitely different from the conventional way. In this way, both of the auxiliary
winding and the extra sensing pin on the control IC can be removed. Following the description of
the proposed circuit are the insight into the operating principle, the design equations, and an
example application of an 8-W LED bulb.
Finally, the experimental results verify the accuracy of the theoretical analysesFor the
sake of improving the aforementioned disadvantages and reducing the driver cost, there are
several topologies for LED driver circuits that have been developed consequently. Although
these LED driver circuits have many advantages, their efficiencies are usually not good enough
(about 80%).
In order to enhance the power efficiency, quasi-resonant (QR) valley-switching is one of
the most familiar methods. The QR valley-switching is achieved by the L−C resonant tank,
which is composed of the main inductance and the parasitic capacitance of the power MOSFET.
In this way, the power MOSFET will be switched on once the drain-tosource voltage resonates to
the lowest value to minimize the switching loss, and this technique is called valley-switching

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EXISTING SYSTEM:
In order to enhance the power efficiency, quasi-resonant (QR) valley-switching is one of
the most familiar methods. The QR valley-switching is achieved by the L−C resonant tank,
which is composed of the main inductance and the parasitic capacitance of the power MOSFET.
In this way, the power MOSFET will be switched on once the drain-to-source voltage resonates
to the lowest value to minimize the switching loss, and this technique is called valley-switching

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PROPOSED SYSTEM:
In order to further simplify the bill of material cost and size of the LED driver circuit, this
paper proposes a novel control scheme of QR valley-switching for a high-PF ac-to-dc LED
driver circuit. The proposed control circuit can innovatively sense the QR valley signal from the
current sense, and it is definitely different from the conventional way. In this way, both of the
auxiliary winding and the extra sensing pin on the control IC can be removed.

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ADVANTAGES:
 Leading to a higher efficiency.
 The auxiliary winding can be eliminated to minimize the magnetic core size and cost.
 The cost and size of the final controller would be reasonable and competitive

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BLOCK DIAGRAM:

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TOOLS AND SOFTWARE USED:
 MPLAB – microcontroller programming.
 ORCAD – circuit layout.
 MATLAB/Simulink – Simulation

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APPLICATIONS:
 Light-emitting diodes (LEDs).

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CONCLUSION:
A novel QR valley-switching scheme for a high-PF ac-todc LED driver circuit has been
presented. Since the proposed QR valley-switching scheme can detect the valley from current
sense resistance, the auxiliary winding can be eliminated to minimize the magnetic core size and
cost. The optimal design of circuit parameters ensures that the circuit can achieve the enuine
feature of QR valley-switching, leading to a higher efficiency. A prototype circuit designed for
an 8-W LED bulb is implemented and measured to verify the theoretical analyses. The
experimental results show that the prototype circuit meets the design targets. Over the universal
input line voltage, a PF higher than 0.93 and a THD less than 23% can be achieved. With the
proposed QR valley-switching process, the LED driver circuit achieves a maximum efficiency of
91.5%.

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REFERENCES:
[1] D. G. Lamar et al., “Design-oriented analysis and performance evaluation of a low-cost high-
brightness LED driver based on flyback power factor corrector,” IEEE Trans. Ind. Electron., vol.
60, no. 7, pp. 2614–2626, Jun. 2013.
[2] Y. C. Li and C. L. Chen, “A novel single-stage high-power-factor ac-todc LED driving
circuit with leakage inductance energy recycling,” IEEE Trans. Ind. Electron., vol. 59, no. 2, pp.
793–802, Feb. 2012.
[3] Y. C. Li and C. C. Chen, “A novel primary-side regulation scheme for single-stage high-
power-factor ac–dc LED driving circuit,” IEEE Trans. Ind. Electron., vol. 60, no. 11, pp. 4978–
4986, Nov. 2013.
[4] S. Jung and G. Cho, “Transformer coupled recycle snubber for highefficiency offline isolated
LED driver with on-chip primary-side power regulation,” IEEE Trans. Ind. Electron., vol. 61, no.
12, pp. 6710–6719, Dec. 2014.
[5] C. Moo, Y. Chen, and W. Yang, “An efficient driver for dimmable LED lighting,” IEEE
Trans. Power Electron., vol. 27, no. 11, pp. 4613–4618, Nov. 2012

A novel control scheme of quasi resonant valley-switching for high-power-factor ac-to-dc led drivers

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A novel control scheme of quasi resonant valley-switching for high-power-factor ac-to-dc led drivers