Download Abstract—In order to obtain sufficient luminance and achieve

An LED Driver With Dynamic High-Frequency Sinusoidal
Bus Voltage Regulation for Multistring Applications
Abstract
This paper presents an LED driver circuit consisting of resonant
inverter and several LCL-T resonant rectifiers. In order to obtain sufficient
luminance and achieve high reliability, light-emitting diodes (LEDs) are usually
arranged in parallel strings in many high-power applications.
Light-emitting diode (LED) are high efficiency and long lifetime when
compared with the existing conventional lighting source. Since current imbalance
should be avoided among the parallel LED strings, a multichannel constant current
LED driver with dynamic highfrequency sinusoidal voltage regulation is proposed
in this paper. The proposed driver is composed of one resonant inverter and
several LCL-T resonant rectifiers. The number of the rectifiers equals to that of the
LED strings. The rectifier whose output current is sensed and closed-loop
controlled is called master rectifier and all the others slave rectifiers. The resonant
inverter is used to convert dc voltage into high-frequency sinusoidal bus voltage
and the LCL-T resonant rectifiers are included to drive LED strings with constant
current.
The amplitude of the high-frequency sinusoidal bus voltage is
dynamically regulated to ensure the output current of the master resonant rectifier
to be constant by a closed-loop controller. Since the output current of the slave
rectifier is linear with the amplitude of the bus voltage as the master rectifier, there
are not any auxiliary circuits included in the slave rectifier while the output current
balancing is achieved. Finally, a 200-W prototype with one master and fifteen
slave rectifiers is built to verify the performance of the proposed driver
Existing Methods and It’s Drawbacks
1. Active method
Constant current regulator
 Linear type
 Switched type
Drawbacks of Active Method
Linear type-High power loses and poor efficiency
Switched type-complex and high cost
2. Passive current Balancing method
 Resister
 Capacitor
 Hybrid passive current balancing method
Drawbacks of Passive Method
Resister-Ballast resistor in series with each LED string to minimize the current
difference will lead to large unnecessary loss of energy
Capacitor-Required more transformers
Hybrid passive current balancing method-High cost, limited output and
seven passive components needed to achieve one output channel
Proposed Method
 LED driver circuit consisting of one resonant inverter and several LCLT resonant rectifiers.
Advantages of proposed system
 Full load and light load efficiency are maximized.
 Protects the system during full load operation.
 It can easily achieve the multichannel constant current output.
 High efficiency due to its soft switching characteristics.
 LED has long life time when compared with the existing conventional
lighting.
Applications
 Energy consumption.
 Automotive lighting.
 Architectural lighting.
 Display backlighting.
 LED based street light.
 Low loss led drive improves a system green foot point by boosting
efficiency and battery life.