6A RGB LED Driver Reference De
6a rgb led driver reference design for a portable projector
abstract: this is 6a step-down led driver based on the max16821 device. this circuit drives a single led. this application note includes the circuit specifications, circuit schematic, and circuit description and performance.
introductionthis is a reference design for a 6a step-down led driver for a portable projector. the reference design is based on the max16821, a pwm hb led driver. this circuit drives a single led; three max16821 devices are required to drive rgb leds.
led driver specifications input supply voltage (vin): 10v to 15v output voltage (vled): 4.5v to 6v output current (iled): 1.5a to 6a with analog control analog control voltage: 1.1v to 2.8v for 1.5a to 6a maximum led on duty cycle: 50% maximum led current rise/fall times: < 1µs maximum led current ripple: < 15% at 6a inputs vin (j1 and j2 vin+, j3 and j4 gnd): 10v to 15v input power supply on/off (j8): leave open or drive +5v to enable the driver. short for disabling the board. pwm input (j7): dimming pwm input. connect a pwm signal with 3v to 5v amplitude. the source should provide rise/fall times less than 500ns with a 300pf load so that the pwm input can drive q1 and q7. as output can rise/fall within 1µs, any pwm period three to four times higher than 1µs can be used. led current control (j6): led current adjust input. apply 1.1v to 2.8v to adjust led current from 1.5a to 5a. outputs led+ (j9, j10): connect anode of led. led- (j11, j12): connect cathode of led. inductor current output (j5): provides a signal proportional to the led current. the voltage at outv will be 135x the voltage across r9.
more detailed image (pdf, 2.23mb)
figure 1. the led driver board features the max16821.
more detailed image (pdf, 2.63mb)
figure 2. schematic of the led driver board.
circuit descriptionthis led driver steps down a 10v to 15v input supply voltage to drive a constant current to an led with a 4.5v to 6v forward voltage. the max16821 pwm hb led driver is used to implement the step-down converter. since the average inductor current equals the led current, the average inductor current can be controlled to drive a constant current to an led. the switching frequency is set to 300khz by r6 (200kω).
two control loops are present: an inner current loop controls the inductor current based on the output of the outer voltage loop; the outer voltage loop programs the inner current loop to control the led current. the outer voltage loop monitors the outv pin and the output of u1 to generate the eaout signal. that eaout signal controls the inner current loop and, thus, the inductor current.
analog led current controlan op amp, u1, takes an analog input from 1.1v to 2.8v and drives the sense+ input of the max16821 to adjust the led current from 1.5a to 6a. when 6a is driven to the led, the reference voltage and the resistive-dividers connected to u1 produce about 20mv (higher than the worst-case vol) at u1's output. a voltage of 2.8v at the analog control input produces this output voltage. when the led current reaches 6a, the resistive-divider, comprised of r1 and r22, adds a fraction of current-sense signal at outv to the output of u1; r1 and r22 produce a voltage equal to the 100mv outer-loop reference at the sense+ input. note that the outv signal is the amplified version of the current-sense signal across r9 and r18 with an amplification of 135v/v. as the voltage at the analog control input is reduced from 2.8v, the output of u1 increases linearly from 20mv. a higher voltage at the output of u1 takes the sense+ input to 100mv at a lower led current. when the analog control input reduces to about 1.1v, the output of u1 increases to 80mv and the led current reduces to 1.5a.
pwm dimmingduring the pwm off time, the mosfet q9 connected across the led output is turned on, thus short-circuiting the led. the led current reduces to zero, depending on the turn-on time (much less than 1µs for this design) of q1. inductor current is maintained throughout the pwm off period. q1 is turned off and the inductor current charges the output capacitor at the beginning of the pwm on time. once the output voltage reaches the led's cut-in voltage, the led current starts to rise. the time required for the led current to rise from 0a to the full value depends on several factors: the inductor current, the value of the output capacitor, and the change in the led forward voltage from cut-in to full current. this reference design meets the 6a to led+ and led- with shortest possible leads to reduce inductance. if leads need to be long, then twisted-pair wires can be used. keep j5 and j8 open. turn on ps2 and apply 1.1v. increase ps1 gradually to 10v. the led will turn on with a 1.5a continuous current. connect a 30% duty-cycle pulse with 3v to 5v amplitude to pwm. the led current will turn on and off with the pwm signal. increase ps2 from 1.1v to 2.8v. the led current will rise from 1.5a to 6a during pwm on.
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abstract: this is 6a step-down led driver based on the max16821 device. this circuit drives a single led. this application note includes the circuit specifications, circuit schematic, and circuit description and performance.
introductionthis is a reference design for a 6a step-down led driver for a portable projector. the reference design is based on the max16821, a pwm hb led driver. this circuit drives a single led; three max16821 devices are required to drive rgb leds.
led driver specifications input supply voltage (vin): 10v to 15v output voltage (vled): 4.5v to 6v output current (iled): 1.5a to 6a with analog control analog control voltage: 1.1v to 2.8v for 1.5a to 6a maximum led on duty cycle: 50% maximum led current rise/fall times: < 1µs maximum led current ripple: < 15% at 6a inputs vin (j1 and j2 vin+, j3 and j4 gnd): 10v to 15v input power supply on/off (j8): leave open or drive +5v to enable the driver. short for disabling the board. pwm input (j7): dimming pwm input. connect a pwm signal with 3v to 5v amplitude. the source should provide rise/fall times less than 500ns with a 300pf load so that the pwm input can drive q1 and q7. as output can rise/fall within 1µs, any pwm period three to four times higher than 1µs can be used. led current control (j6): led current adjust input. apply 1.1v to 2.8v to adjust led current from 1.5a to 5a. outputs led+ (j9, j10): connect anode of led. led- (j11, j12): connect cathode of led. inductor current output (j5): provides a signal proportional to the led current. the voltage at outv will be 135x the voltage across r9.
more detailed image (pdf, 2.23mb)
figure 1. the led driver board features the max16821.
more detailed image (pdf, 2.63mb)
figure 2. schematic of the led driver board.
circuit descriptionthis led driver steps down a 10v to 15v input supply voltage to drive a constant current to an led with a 4.5v to 6v forward voltage. the max16821 pwm hb led driver is used to implement the step-down converter. since the average inductor current equals the led current, the average inductor current can be controlled to drive a constant current to an led. the switching frequency is set to 300khz by r6 (200kω).
two control loops are present: an inner current loop controls the inductor current based on the output of the outer voltage loop; the outer voltage loop programs the inner current loop to control the led current. the outer voltage loop monitors the outv pin and the output of u1 to generate the eaout signal. that eaout signal controls the inner current loop and, thus, the inductor current.
analog led current controlan op amp, u1, takes an analog input from 1.1v to 2.8v and drives the sense+ input of the max16821 to adjust the led current from 1.5a to 6a. when 6a is driven to the led, the reference voltage and the resistive-dividers connected to u1 produce about 20mv (higher than the worst-case vol) at u1's output. a voltage of 2.8v at the analog control input produces this output voltage. when the led current reaches 6a, the resistive-divider, comprised of r1 and r22, adds a fraction of current-sense signal at outv to the output of u1; r1 and r22 produce a voltage equal to the 100mv outer-loop reference at the sense+ input. note that the outv signal is the amplified version of the current-sense signal across r9 and r18 with an amplification of 135v/v. as the voltage at the analog control input is reduced from 2.8v, the output of u1 increases linearly from 20mv. a higher voltage at the output of u1 takes the sense+ input to 100mv at a lower led current. when the analog control input reduces to about 1.1v, the output of u1 increases to 80mv and the led current reduces to 1.5a.
pwm dimmingduring the pwm off time, the mosfet q9 connected across the led output is turned on, thus short-circuiting the led. the led current reduces to zero, depending on the turn-on time (much less than 1µs for this design) of q1. inductor current is maintained throughout the pwm off period. q1 is turned off and the inductor current charges the output capacitor at the beginning of the pwm on time. once the output voltage reaches the led's cut-in voltage, the led current starts to rise. the time required for the led current to rise from 0a to the full value depends on several factors: the inductor current, the value of the output capacitor, and the change in the led forward voltage from cut-in to full current. this reference design meets the 6a to led+ and led- with shortest possible leads to reduce inductance. if leads need to be long, then twisted-pair wires can be used. keep j5 and j8 open. turn on ps2 and apply 1.1v. increase ps1 gradually to 10v. the led will turn on with a 1.5a continuous current. connect a 30% duty-cycle pulse with 3v to 5v amplitude to pwm. the led current will turn on and off with the pwm signal. increase ps2 from 1.1v to 2.8v. the led current will rise from 1.5a to 6a during pwm on.
Broadcom上季度营收92.95亿美元，同比增长4%
2018年内存行业将推动半导体收入达4510亿美元 较比去年增长7.5%
Infineon推出超低电容及四线 ESD5V3U4U-HD
Intel展示新一代酷睿 基于10nm工艺打造2019年末推出
MAX15090/MAX15090B热插拔方案在阻性负载低压应用中的应用
6A RGB LED Driver Reference De
布局电力行业，巡检机器人的优势何在？
基于新一代SoC SH7264的图形仪表板开发平台
海上组合惯导的介绍（关于惯导在海上的应用）
以KaggleDays数据集为例，编码方法介绍
Pyintervals 超简单解决你的数值区间处理问题
视觉引导的机器人降低了元件生产成本提高了产品质量
2022年全球汽车产量、缺芯和新能源汽车渗透率
存储系统中的智能在线压缩技术
“光伏＋”的应用场景同样蕴含巨大的市场
3GPP R16标准冻结和5G商用的开启将会催熟更多的新兴业务
密钥管理系统概述_密钥管理系统架构图
物联网传感器与农业融合，汇总十项科研新进展
气体检测仪有哪些使用误区，有什么注意事项
重点讲解Send与Sync相关的并发知识