Download a novel wall-switched step-dimming concept in led

A NOVEL WALL-SWITCHED STEP-DIMMING CONCEPT IN LED
LIGHTING SYSTEMS USING PFC ZETA CONVERTER
ABSTRACT:
This paper presents the design, simulation, and implementation of a non-isolated
discontinuous conduction mode operated Zeta-converter-based light-emitting diode
(LED) driver with the novel wall-switched step dimming concept to achieve power
quality improvement at universal ac mains.
The power-factor-corrected Zeta converter maintains constant output current to an
LED load of 26 W and conserves the power quality requirements as per IEC
61000-3-2 for class C equipment with high efficiency.
Moreover, to obtain cost benefit and size reduction, this converter utilizes reduced
control circuitry for general-purpose LED lighting solutions. A cost-effective
single-level dimming concept is implemented with current injection technique
using a Zeta converter.
A prototype is developed using AP1682, which utilizes pulse frequency
modulation technique to regulate the output current for improving the input power
factor and low total harmonic distortion (THD) of the input current.
At full load and rated voltage of 220 V, the measured input power factor is 0.993
and current THD is 2.81% with an efficiency of 90.51%.
INTRODUCTION:
Owing to the advantages of LED solutions in lighting industries, this is an
attractive field of study and research. The fundamental requirement of an LED is
the constant drive current irrespective of AC mains conditions and the number of
LEDs connected in a load. Increasing drive current can increase junction
temperature (Tj) which reduces light output thus the overall efficacy of the system.
In recent years, single stage DC-DC power converters have been widely used for
PFC as well as regulation for an LED load. Among the different DC-DC
converters, six basic topologies have wide acceptance in industry viz. buck, boost,
buck-boost, Cuk, SEPIC (Single-Ended Primary Inductor Converter) and Zeta
converter.
Except Zeta converter, all other converters are widely studied and used for PFC
(Power Factor Correction) operation of LED power supplies in different modes of
operation such as CCM (Continuous Conduction Mode), BCM (Boundary
Conduction Mode) and DCM (Discontinuous Conduction Mode) [3-8].
The research on lighting applications using the Zeta converter has been unexplored
since long time.
This paper presents an attractive application of the Zeta converter in low-power
LED lighting systems with high power factor and very low harmonic distortions
over the universal ac
mains with a novel current injection step-dimming concept.
The preference of the Zeta converter has also emerged from the limitations
observed in other converters. The buck converter is essentially the cheapest
converter among all, but it serves effectively only when the output dc voltage is
much lower than the input ac voltage.
Even at the time of ac mains crossover, it exhibits higher distortions in ac mains
current. Therefore, this converter is not a good choice as a PFC in such
applications. The boost converter, on the other hand, presents better power quality
performance with higher efficiency, and this has been extensively utilized in
industries.
However, this converter provides a higher output voltage than its input voltage for
an efficient PFC operation. LEDs are generally low-voltage devices.
EXISTING SYSTEM:
The Zeta converter has discontinuous input current in comparison to SEPIC
and Cuk converters, due to its configuration, but it has less ripple contents at
output than a SEPIC converter.
This reduced ripple output is very much recommended to power certain
types of loads such as LEDs which are extremely sensitive to the voltage
variations. Owing to the nature of discontinuous current at output, SEPIC converter
requires bigger DC link capacitor (E-cap) hence more cost as compared to Zeta
converter to attain the same permissible ripple contents to the LED load over the
universal AC mains
PROPOSED SYSTEM:
This paper presents an attractive application of Zeta converter in low power
LED lighting systems with high power factor and very low harmonic distortions
over the universal AC mains with a novel current injection step-dimming concept.
For low power application, DCM is preferred due to its inherent PFC capabilities
with reduced control circuitry.
ADVANTAGES:
 PFM offers better regulation in light load conditions and reduces switching
losses by sometime skipping pulses when not required
 BLOCK DIAGRAM:
TOOLS AND SOFTWARE USED:
 MPLAB – microcontroller programming.
 ORCAD – circuit layout.
 MATLAB/Simulink – Simulation
APPLICATIONS:
 Light Emitting Diodes (LEDs).
CONCLUSION:
The non-isolated Zeta-converter-based LED driver has shown PQ
improvement using the PFM technique at universal ac mains. In low power, it is
quite difficult to maintain high PF, but the Zeta converter has sustained the input
PF almost unity and input current harmonic contents well under the limits of IEC
61000-3-2 for class C equipment over universal ac mains with high efficiency. The
converter is also the best suited for an LED driver with constant-current peration
using the PFM technique and has provided constant-voltage constant-current
control using the PSR scheme. A novel low-cost wall-switched step-dimming
retrofit solution is implemented by utilizing the non-isolated Zeta converter. The
performance of the driver at 50% dimming condition has been found quite well in
terms of power quality indices and efficiency. The proposed low-cost dimming
concept is established, which could be helpful in designing an industrial platform
for future offline LED systems.
REFERENCES:
[1] J. Y. Tsao, “Solid-state lighting: Lamps, chips, and materials for tomorrow,”
IEEE Circuits Devices Mag., vol. 20, no. 3, pp. 28–37, May/Jun. 2004
.
[2] T. Komine and M. Nakagawa, “Fundamental analysis for visible-light
communication system using LED lights,” IEEE Trans. Consum. Electron., vol.
50, no. 1, pp. 100–107, Feb. 2004.
[3] C. Chun-An, C. Hung-Liang, and C. Tsung-Yuan, “A novel single-stage highpower-factor LED street-lighting driver with coupled inductors,” IEEE Trans. Ind.
Appl., vol. 50, no. 5, pp. 3037–3045, Sep./Oct. 2014.
[4] L. Jun-Young and C. Hyung-Jun, “6.6-kW onboard charger design using DCM
PFC converter with harmonic modulation technique and twostage dc/dc
converter,” IEEE Trans. Ind. Electron., vol. 61, no. 3, pp. 1243–1252, Mar. 2014.
[5] 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, Jul. 2013.