micrel 公司的mic3203降壓恒流高亮度led(hbled)驅動器,輸入電壓從4.5v到42v,效率大于90%,led的電流精度±5%,開關頻率高達1.5mhz,主要用在建筑物,工業和環境照明,led燈,指示器和緊急照明,街道照明以及12v照明系統.本文介紹了mic3203主要特性, 方框圖, 降壓led驅動器電路和mic3203/mic3203-1 評估板電路圖與材料清單(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 應用:

• 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)


圖1.mic3203/mic3203-1方框圖

圖2.mic3203降壓led驅動器電路

mic3203/mic3203-1 評估板

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℃.


圖3.mic3203/mic3203-1 評估板電路圖

mic3203/mic3203-1評估板材料清單(bom):