An efficient self-configurable driver for color light emitting diode

To arrange an accurate load current for the different sets of color LEDs, an efficient LED driver must facilitate the current sharing among the LED strings using a constant current source. Effective utilization of power in an LED string is vital for display panels as it defines the magnitude of the undesirable phenomenon of flickering switching. An efficient and dimmable LED driver suitable for LED back-light drivers in the LED display panel is presented in this thesis. This thesis proposed a color LEDs driver with a self-configuration of the enhanced current mirror in multiple LED strings. In this proposed work, the load currents have been efficiently balanced among the identical and unequal loads of color LEDs. In a traditional current mirror, the buck converter is linked with a fixed current load. Nonetheless, in the proposed improved self-adjustable current mirror, the variation of LEDs load string could be addressed using a single buck converter. The improvement is based on the combinational circuits of transistor and op-amp with proper scheme biasing. The improved dimming circuit is then proposed for exploiting the range of dimming at the string and module level. Furthermore, the proposed current-balancing circuits excluded a separate power supply to control current in different load strings of LEDs (red/green/blue). Since the approach circuit is identical and modular, it could be scaled to any number of parallel current sources. The different bi-level pulsating driving have been performed to reduce the loss while running the LEDs at the high peak current. It is to create two driving parameters, which are the low/high current levels (pulse width modulation) and associated duty cycles, in having the capability to control luminosity effectively. It can be seen, the previous techniques had improved the luminous efficacy of LEDs by using n-level driving techniques but at the trade-off of losing efficiency with the introduction of resistors (variables in series) to create a bi-level phenomenon for the driver. Therefore, this thesis proposes to replace the resistors with the new approach dimming circuit to get a significant improvement in the overall system’s efficiency that can assist to dim an individual LEDs string based on designated color (red or green or blue) LEDs. Meanwhile, in improving illuminance through dimming, the hybridization of pulse width modulated (PWM) and amplitude modulated (AM) has been proposed. As a result, the proposed LEDs driver has shown effective current balancing through the color LEDs string with exploiting a large dimming range. The illumination analysis has also shown a significantly higher when compared with PWM (bi-level pulsating). The computation efficiency for red, green, and blue LEDs strings around range 92% to 99%

Self-Configurable Current-Mirror Technique for Parallel RGB Light-Emitting Diodes (LEDs) Strings

Traditional current-mirror circuits require buck converter to deal with one fixed current load. This paper deals with improved self-adjustable current-mirror methods that can address different LED loads under different conditions with the help of one buck converter. The operating principle revolves around a dynamic and self-configurable combinational circuit of transistor and op-amp based current balancing circuit, along with their op-amp based dimming circuits. The proposed circuit guarantees uniformity in the outputs of the circuit. This scheme of current-balancing circuits omitted the need for separate power supply to control the load currents through different kinds of LEDs, i.e. RGB LEDs. The proposed methods are identical and modular, which can be scaled to any number of parallel current sources. The principle methodology has been successfully tested in Simulink environment to verify the current balancing of parallel LED strings

An efficient color LED driver based on self-configuration current mirror circuit

The string channel of Color LED driver with precise current balancing is proposed. It is noted that to drive a multiple LEDs string is by using a proper current source, due to the level of the brightness LED depends on the quantity of the current flows. In the production of LEDs, the variation in the forward voltage for each LED has been found significantly high. This variation causes different levels of brightness in LEDs. Then, controlling load current of LED by using a resistor to limit the LED current flowing is considered by associated with the forward voltage, instantly. Current sources have been designed to become immune to the above problem since it regulates the current, and not the voltage which flows through the LEDs. Hence, constant current source is the essential requirement to drive the LEDs. Besides, it is complex for color LEDs, dependent on the number of control nodes and dimming configuration. To arrange an accurate load current for the different sets of string color LEDs, the efficient LED driver is required, in which the current sharing is complement to each LED strings. Therefore, this paper suggests a color LED driver with self-configuration of enhanced current mirrors in multiple LED strings. The load currents have been efficiently balanced among the identical loads and unequal loads. The comparable efficiency of the string color LEDs losses has been shown thoroughly

An efficient digitally controlled of RGB driver for LED pixels

The RGB LEDs are used for producing different colours and different intensities. These LEDs are generally driven by constant current sources because their colours and brightness are directly related to their forward current. This paper proposes a digital control of the DC-DC converter to provide accurate currents for the RGB LED driver for achieving a high efficiency and accuracy of load current. The load current accuracy is an essential index for a high performance LED driver. The proposed maintains the current source for the minimum drive of the voltage across the LEDs which lead to reduce power dissipation in the MOSFET and increase efficiency in the LEDs’ string. The RGB LEDs use three different voltage sources as each RGB colour requires different drive voltages. The proposed LED driver system is also able to dim LEDs in the pixel through pulse width modulation signals as dimming signals. These dimming signals also work as a reference voltage for the current controllers to regulate the load current. The proposed model is simulated in MATLAB/Simulink environment, and the results are verified accordingly. With 12V supply voltage, the efficiency of RGB LEDs are 93%, 97% and 97% respectively

Comparative analysis for LED driver with analog and digital controllers

The trend of utilizing light emitting diodes (LEDs) in a number of applications has attracted the attention of many researchers, to study its applications. This article investigates the performance analysis of the dc-dc converter systems based on analog and digital controllers for a low voltage dc-dc buck converter, to drive strings of LEDs at different conditions, to judge system’s robust performances. This particular converter comprises of a single controller, working with a voltage control feedback system, in a continuous conduction mode. The analog and digital type- 3 controllers are designed for the said system while using standard frequency response techniques. Simulations are shown to validate the design and the response of these controllers under various dynamic load conditions

A Robust Driver for RGB LEDs

For running applications based on RGB LEDs, a dc-dc buck converter associated with linear control is mostly used to manage the constant current of LED. In this paper, the driver to run RGB LEDs gives 180 mA constant outputs current and a PWM control scheme has been utilized, which determines the desired brightness levels with a dimming frequency of 10000 Hz. Previously there used to be a dimming option for dimming each array of LED color, through the dimming controller circuit; approximately 93%, 90% 93% efficiencies, were found for the green, red and blue color LEDs' arrays respectively. A digital controller based on PID controller has been created, with the option of using digital dimming by using current mirroring with a transistor (for the intent of switching system). The proposed LED driver system contains the constant source of current to maintain the small drive voltage across the LEDs which lead in the reduction of power dissipation in the transistor, i.e., NPN, which eventually increases the efficiency of the whole system in return. With the application of the 12V supply voltage, the efficiencies of RGB LEDs are found up to 98.94%, 99.37%, and 99.37% correspondingly