NS LM3423环境光自适应LED驱动方案(图)
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NS的LM3421/LM3423是恒流LED驱动器的N沟控制器,可配置成降压,升压,降-升压(反激)或SEPIC,输入电压可高达75V,非常适合各种情况下的LED照明应用. 采用LM3423的环境光自适应LED驱动器采用4.5V-12V的电池输入,在15-20V时LED保持100mA的恒流,效率高达85%,PWM标LED调光高达25kHz,可使LED的亮度正比与环境光,从而延长了电池使用寿命.本文介绍了LM3421/LM3423的主要特性,方框图以及相应的应用电路.同时还介绍了采用LM3423的环境光自适应LED驱动器的主要特性,详细的电路图和材料清单(BOM).
LM3421, LM3423: N-ChannEL Controllers for Constant Current LED Drivers
The LM3421/LM3423 devices are versatile high voltage LED driver controllers. With the capability to be configured in a Buck, Boost, Buck-Boost (Flyback), or SEPIC topology, and an input operating voltage rating of 75V, these controllers are ideal for illuminating LEDs in a very diverse, large family of applications.
Adjustable high-side current sense with a typical sense voltage of 100mV allows for tight regulation of the LED current with the highest efficiency possible. Output LED current regulation is based on peak current-mode control with predictive Off-Time Control. This method of control eases the design of loop compensation while providing inherent input voltage feed-forward compensation.
The LM3421/LM3423 include a high-voltage startup regulator that operates over a wide input range of 4.5V to 75V. The internal PWM controller is designed for adjustable switching frequencies of up to 2.0MHz, thus enabling compact solutions.
Additional features include: zero current shutdown, precision reference, logic compatible DIM input suitable for fast PWM dimming, cycle-by-cycle current limit, and thermal
shutdown.
The LM3423 also includes an LED output status flag, a fault flag, a programmable fault timer, and a logic input to select the polarity of the dimming output driver.
LM3421/LM3423主要特性:
■VIN range from 4.5V to 75V
■2% Internal reference voltage (1.235V)
■urrent sense voltage adjustable from 20mV
■High-side current sensing
■2Ω MOSFET gate driver
■Dimming MOSFET gate driver
■Input under-voltage protection
■Over-voltage protection
■Low shutdown current, IQ < 1μA
■Fast (50kHz) PWM dimming
■Cycle-by-cycle current limit
■Programmable switching frequency
■LED output status flag (LM3423 only)
■Fault timer pin (LM3423 only)
■TSSOP EP 16-lead package (LM3421)
■TSSOP EP 20-lead package (LM3423)
LM3421/LM3423应用:
■LED Drivers
■Constant-Current Buck-Boost Regulator
■Constant-Current Boost Regulator
■Constant-Current Flyback Regulator
■Constant-Current SEPIC Regulator
■Thermo-Electric Cooler (Peltier) Driver
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