The current rating of the Mosfet switch, together with the step up ratio, will determine the maximum load current, and the Mosfet voltage rating will determine the maximum output voltage capability. Efficiency is stated at up to 85% across the 2.7 to 5.5 V VIN range. For larger displays, driving up to eleven series white LEDs, a well-proven solution is the LM3530 from Texas Instruments. There are many vendors of such devices, several of which have produced some useful application guides to help designers minimize power consumption and improve efficiency. click site
Selecting a Schottky diode with a low forward turn-on voltage (VF), TI advises, will improve boost efficiency; although designers are warned that low VF Schottky diodes are usually larger than those Further, the high duty cycles associated with series backlight drivers (>80%) will minimize the impact of a low VF diode, as the device is only conducting for a small percentage of Boost is best Constant current boost converters are generally regarded as the optimum power-saving devices for powering LEDs used for display backlighting in battery-operated applications. While watching video content, for example, a dynamic backlight controller can automatically adjust the brightness levels in order to save power.
\\ Power Management ICs \\ LED Drivers \\ Inductive Boost LED Drivers Inductive Boost LED Drivers Semtech manufactures an extensive line of inductive LED driver ICs for LCD panel backlights serving Dynamic backlighting For power hungry portable devices, such as smartphones, manufacturers are increasingly incorporating ambient light sensors: the darker the environment, the less light output required for the display. However, a smaller inductor will typically have a higher resistance compared to a larger one with the same inductance value.
Related Product Highlight LM3530 White LED Driver The LM3530 is the industry's smallest white LED driver with dynamic display backlight control. Conclusion Maximizing battery life remains the overarching concern of designers of portable devices destined for the burgeoning IoT market. Constant current converters are important because LEDs need to be driven with a specific current to maintain a specific light output. Diodes Inc Share This Article Share This Article Related Product Training Modules Lighting- LED Lighting Driver Solutions Designing LED lighting solutions with TI's products is easy and fast with a wide selection of
The result is a more uniform transition between brightness levels. Led Diodes Bulk Let’s take a brief look at a few devices suitable for powering LEDs for backlighting displays and keyboards in battery-portable products. Richtek, another power management specialist, explains in an Application Note entitled: Power Management Introduction2, inductive boost converters operate by charging an inductor via an internal Mosfet switch, and discharging the inductor In this mode, the inductor must be between 10 and 22 µH.
Further advances in dimming techniques have resulted in TI’s LM3697; again using a boost converter to drive up to three parallel high-voltage LED strings, but this time featuring 11-bit exponential dimming. Buck-boost for wearables Wearable and ultra-low-power devices can benefit from a different approach. Minimizing the power needed to light the display is a key objective. The LED backlight driver alone can use up to 40%, making it a prime target for power conservation efforts.
In a series converter, a single current sink is required to control the current through each LED string. The company’s RT6150A/B is worth investigating here. Constant Current Boost Led Driver An external PWM input is provided for linear brightness adjustments. Led Driver Circuit Inductive Boost LED Drivers SC440A High Efficiency Integrated Driver for 6-Strings of 30mA LEDs SC441A High Efficiency Integrated Driver for 4-Strings of 150mA LEDs - AEC-Q100 Qualified SC441C High
Richtek summarizes the key parameters for selecting LED drivers as: input voltage, LED string voltage and LED string current, single/multi-string LEDs and dimming requirements. http://vinaprosoft.com/led-driver/led-boost-driver-ic.php Their high-efficiency and high-switching frequencies make them well suited to modern consumer equipment.Diodes' linear LED drivers provide a simple cost-effective solution to driving low-current, high-brightness LEDs.Licensed LED Partners Off-Line LED Drivers Richtek recommends either a charge pump device, such as the RT9361A requiring no external inductor, or a buck-boost topology. LED current, adjustable via an I2C compatible interface, operates from 0 to 29.5 mA with 127 current steps and eight maximum current levels. Diode Led
In this case, the brightness levels depend on the type of information being displayed. Figure 1: Dynamic backlight control uses dimming to save battery power, such as when using a smartphone in the dark. TI points out that a designer could, for example, set up use cases with five brightness levels, corresponding to sunlight, cloudy outdoors, bright indoors, dim room and night time. http://vinaprosoft.com/led-driver/led-boost-driver.php The power drawn from the battery can be reduced significantly by this means.
Texas Instruments provides design in many of its device datasheets and also in an article: A holistic approach to reducing backlight power consumption1. This prevents current variations in the LED string due to dips in the input voltage and/or the output voltage ripple caused by the charge/discharge cycle of the output capacitor. XO Programmable XO Build Programmable XO Part Number SSXO Ultra Low Jitter XO VCXO/TCXO/VCCTCXO VCXO TCXO / VCTCXO Xtals/Crystals Standard Xtal Parts Interface Universal Level Shifter / Voltage Translation (ULS) UART
The transition from inductor charge to discharge will reverse the voltage across the inductor, thereby stepping up the voltage higher than VIN. Interestingly, the device offers two switching frequency settings. Integrated switch LED drivers are capable of delivering LED currents up to 1.5A. Boost converters are used to step-up the input voltage to a higher output voltage.
This is not a functioning page on our site. In all of these cases, the LED drivers should offer flexible dimming support, requiring the control of the output current, and thereby the LED light output. TI suggests that the inductive boost converter can be optimized by minimizing the on-resistance of the Nmos power switch and the series resistance of the inductor. my review here Uses range from 3W LED flashlights, to bicycle lights, to solar powered architectural lighting.
In some boost converters, the rectifier is integrated as a Mosfet to provide synchronous rectification. A later version, the LM3532, is designed to drive three parallel high-voltage LED strings, at 40 V. There is, inevitably, an impact on picture quality, but the designer can determine the optimum point between reducing power consumption and maintaining picture quality. However, at 1 MHz, efficiency is optimized at higher load conditions, resulting in lower conduction losses in the MOSFETs and inductor.
Intersil is also focusing on power management devices for wearables and recommends buck-boost. With the movement towards the Internet of Things, and the pervasive use of smart devices such as mobile phones for networked control and monitoring purposes, the need for improved power efficiency LED current is regulated (5 to 20 mA in five steps) by setting the current sense resistor, and for accuracy, precision resistors are recommended. Check out the ISL91110, claimed particularly useful for maximizing the energy utilization of single-cell Li-ion batteries that have significant capacity remaining at voltages below the system voltage.
Selecting LED driver ICs that have been optimized for low power and efficiency is a clear start point. This article will consider the contribution that can be made through advanced design and the judicious choice of the LED driver. Reference will be made to the Richtek RT9285 boost converter, ideal for operation from a single cell li-ion battery, and from Texas Instruments, the LM3530 current mode boost converter which can