Led driver circuit ic
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MP3302 is a boost converter IC specifically designed for LED drive applications. The MP3302 can drive 27 LEDs (9 strings of 3 white LEDs in series) from a Lithium ion battery. The IC has internal power MOSFETs for driving the LEDs and has an efficiency of 88%. Switching frequency is 1.3 MHz and the internal current limit is 1.33 A. Other features of the MP3302 are open load shut down, thermal shut down, under voltage lock out etc. Applications of Mp3302 are LED back lights, LED based lighting gadgets etc. Functional block diagram of the MP3302 is shown below ( Fig1). MP3302 functional block diagram The IC uses a constant current, peak current mode step up regulator scheme for regulating the current through the LEDs. At the beginning of each oscillator cycle, the control circuitry switches the power MOSFET ON. For preventing sub harmonic oscillation, a stabilizing ramp signal is added to the current sense amplifiers output and the resultant signal is given to the non inverting input of the PWM comparator. When this resultant voltage is equal to the voltage at the PWM comparator’s inverting input (output voltage of the error amplifier the power MOSFET is switched OFF. The error amplifier’s output is the difference between the feedback voltage and the reference voltage. When the output voltage drops, the feedback voltage also drops and this in increases the output of the error amplifier. This in turn increases duty cycle of the power MOSFET drive signal produced by the control circuitry which increase the duty cycle of the power MOSFET, it conducts more current and the output voltage is regulated. Circuit diagram of a 27 LED driver circuit using MP3302 is shown below ( Fig 2). MP3302 LED driver circuit diagram. MP3302 LED driver IC circuit C1 is the input bypass capacitor and C2 is the output bypass capacitor. Resistor R1 is the feedback resistor and it controls.
LED has established its unshakable position in the backlighting of portable devices. Even in the backlighting for the large-sized LCD panel, it has started to challenge the mainstream CCFL. In lighting, LED is especially popular in the market due to its highlighted features like energy-efficiency, environmental friendliness, long lifetime, and low maintenance. The driver circuit is a crucial and integral part of the LED. Whether in lighting, backlighting or the display panel, the choice of the technical architecture of the driver circuit must correspond to specific applications. The LED lighting mechanism goes as follows: when the forward voltage is applied to both ends, the minority carrier and majority carrier in the semiconductor recombine to release surplus energy, giving off photons. The main functions of the LED drive circuit are to transfer the AC voltage into a constant power supply and match the voltage and current according to the requirements of LED devices. Apart from safety need, the LED driver circuit must also include two other basic features: First, a constant current should be kept as long as it is possible, thus the output current variation is able to be maintained between the range of ±10％ especially when the power supply change goes beyond ±15％range. Here are the reasons for having a constant current driver when using LED as the monitor, other lighting devices or backlighting: 1. To prevent the drive current from exceeding the maximum rate and further affecting its reliability. 2. To meet expected brilliance requirements and ensure the color and brilliance homogeneity of each LED. Second, the driver circuit should keep low power consumption so that the LED system efficiency can remain at a high level. PWM ( Pulse Width Modification) is a traditional light adjusting technology, which uses simple digital pulses to switch on and off LED driver from time.
PRODUCTS SOLUTIONS DESIGN SUPPORT PURCHASE COMPANY Power Management LED Driver ICs Overview New & Featured Circuits Videos Blogs Tech Support Linear Technology has a very broad line of LED driver ICs for automotive, display backlighting, handheld and general lighting applications. They are configured as either Inductorless white LED drivers (for LEDs in parallel or switching regulator based white LED drivers (for LEDs in series). Topologies include boost regulator LED drivers, buck regulator LED drivers, buck-boost LED drivers, SEPIC topology led drivers and more. Regardless of topology, these LED driver ICs offer the highest efficiency, lowest noise, and the smallest footprints. Other features of Linear Technology LED driver include integrated Schottky diodes, accurate LED current matching and multiple output capability. View All LED Driver ICs Quick LED Driver Search Input Vin ( Min) V Vin ( Max) V LED Strings LEDs In Each String Strings String Current A LED Voltage Min LED Voltage V Max LED Voltage V Featured LT String × 50m A, 2 MHz Step- Up LED Driver with ±1.8% Current Matching LT V, 6 A Synchronous Step- Down Regulator with Current Sense and 3μ A Quiescent Current L igh Current Step- Down LED Driver Controller LT VIN LED Controller with Internal PWM Generator LT V 4- Switch Synchronous Buck- Boost LED Driver Controller LT3799 - Offline Isolated Flyback LED Controller with Active PFC View All LTM8042/ LTM8042-1 - μ Module ( Power Module) Boost LED Driver and Current Source LTC3675/ LTC Channel Configurable High Power PMIC LT VIN, 80 VOUT Constant- Current, Constant- Voltage Converter LT3743 - High Current Synchronous Step- Down LED Driver with Three- State Control LT Channel 120m A LED Driver with ±1.5% Current Matching LT3756/ LT3756-1/ LT VIN, 100 VOUT LED Controller LTM V, 1 A.