Micrel MIC3203 HBLED驱动方案
Micrel 公司的MIC3203降压恒流高亮度LED(HBLED)驱动器，输入电压从4.5V到42V，效率大于90%，LED的电流精度±5%，开关频率高达1.5MHz，主要用在建筑物，工业和环境照明，LED灯，指示器和紧急照明，街道照明以及12V照明系统.本文介绍了MIC3203主要特性， 方框图， 降压LED驱动器电路和MIC3203/MIC3203-1 评估板电路图与材料清单(BOM).
High-Brightness LED Driver Controller with High-Side Current Sense
The MIC3203 is a hysteretic， step-down， constant-current， High-Brightness LED (HB LED) driver. It provides an ideal solution for interior/exterior lighting， architectural and ambient lighting， LED bulbs， and other general illumination applications.
The MIC3203 is well suited for lighting applications requiring a wide-input voltage range.
The hysteretic control gives good supply rejection and fast response during load transients and PWM dimming. The high-side current sensing and on-chip current-sense amplifier delivers LED current with ±5% accuracy. An external high-side currentsense resistor is used to set the output current.
The MIC3203 offers a dedicated PWM input (DIM) which enables a wide range of pulsed dimming. A high-frequency switching operation up to 1.5MHz allows the use of smaller external components minimizing space and cost. The MIC3203 offers frequency dither feature for EMI control.
The MIC3203 operates over a junction temperature from 40℃ to +125℃ and is available in an 8-pin SOIC package.
MIC3203 主要特性:
4.5V to 42V input voltage range
High efficiency (>90%)
±5% LED current accuracy
MIC3203: Dither enabled for low EMI
MIC3203-1: Dither disabled
High-side current sense
Dedicated dimming control input
Hysteretic control (no compensation!)
Up to 1.5MHz switching frequency
Adjustable constant LED current
Over-temperature protection
40℃ to +125℃ junction temperature range
MIC3203 应用:
Architectural， industrial， and ambient lighting
LED bulbs
Indicators and emergency lighting
Street lighting
Channel letters
12V lighting systems (MR-16 bulbs， under-cabinet lighting， garden/pathway lighting)
图1.MIC3203/MIC3203-1方框图
图2.MIC3203降压LED驱动器电路
MIC3203/MIC3203-1 评估板
This board enables the evaluation of the MIC3203/MIC3203-1 for 1A LED current. The board is optimized for ease of testing， with all the components on a single side. The device operates from a 4.5V to 42V input voltage range， and controls an external power MOSFET to drive high current LEDs. When the input voltage approaches and crosses UVLO threshold， the internal 5V VCC is regulated and the integrated MOSFET is turned on if EN pin and DIM pin are high.
The inductor current builds up linearly. When the CS pin voltage hits the VCS(MAX) with respect to VIN， the external MOSFET is turned off and the Schottky diode takes over and returns the current to VIN. Then the current through inductor and LEDs starts decreasing. When CS pin hits VCS(MIN)， the external MOSFET is turned on and the cycle repeats.Since the control scheme does not need loop compensation， it makes for a very simple design and avoids problems of instability.
Requirements
This board needs a single bench power source adjustable over the input voltage of 4.5V < VIN < 42V that can provide at least 1A of current. The loads can either be active (electronic load) or passive (LEDs) with the ability to dissipate the maximum load power while keeping accessible surfaces ideally < 70℃.
图3.MIC3203/MIC3203-1 评估板电路图
MIC3203/MIC3203-1评估板材料清单(BOM):
详情请见:
http://www.micrel.com/_PDF/mic3203.pdf
和
http://www.micrel.com/_PDF/Eval-Board/mic3203_eb.pdf
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