浅谈On Semi NCV7692汽车LED灯电流控制的解刨

On Semi公司的NCV7692汽车LED灯电流控制器,采用外接NPN双极器件和反馈电阻来调整驱动LED的电流.单个驱动器使用户能灵活增加单路到多路系统中.专用的调光特性通过PWM输入引脚来实现.当检测到开路或短路时单路驱动器就开关断.LED亮度采用串联在双极晶体管的外接电阻进行编程.单个NCV7692可驱动多个LED串.NCV7692可采用PWM控制,外接可编电流电阻,可选择负温度系统电流控制,开路LED串和短路LED串诊断,多个LED串控制,满足AEC−Q100 规范和PPAP功能.主要用在汽车后组合灯(RCL),日间灯(DRL),雾灯,中央高位刹车灯(CHMSL)阵列,转向灯和其它外部调制应用,通用汽车线性电流LED驱动器.本文介绍了NCV7692主要特性,框图和多种应用框图,以及评估板EVBUM2664主要特性,电路图和评估板EVBUM2664应用电路与PCB设计图.

The NCV7692 is a device which uses an external NPN bipolar device combined with feedback resistor(s) to regulate a current for use in driving LEDs. The target application for this device is automotive rear combination lamps. A single driver gives the user flexibility to add single channels to multichannel systems. A dedicated dimming feature is included via the PWM input pin. The individual driver is turned off when an open load or short circuit is detected.

LED brightness levels are easily programmed using an external resistor in series with the bipolar transistor. The use of the resistor gives the user the flexibility to use the device over a wide range of currents. Multiple strings of LEDs can be operated with a single NCV7692 device. Set back power limit reduces the drive current during overvoltage conditions.

The device is available in a SOIC−8 package.

NCV7692主要特性:

• Constant Current Output for LED String Drive
• External Bipolar Device for Wide Current Range Flexibility
♦ With BCP56 Transistor, Can Drive Multiple Strings Concurrently (ref. Datasheet Info)
• External Programming Current Resistor
• Pulse Width Modulation (PWM) Control
• Negative Temperature Coefficient Current Control Option
• Open LED String Diagnostic
• Short−Circuit LED String Diagnostic
• Multiple LED String Control
• Overvoltage Set Back Power Limitation
• SOIC−8 Package
• AEC−Q100 Qualified and PPAP Capable
• These are Pb−Free Devices

NCV7692应用:

• Rear Combination Lamps (RCL)
• Daytime Running Lights (DRL)
• Fog Lights
• Center High Mounted Stop Lamps (CHMSL) Arrays
• Turn Signal and Other Externally Modulated Applications
• General Automotive Linear Current LED Driver

图1.NCV7692框图

图2.NCV7692应用框图

图3.NCV7692微处理器控制应用框图

图4.NCV7692输出驱动配置图

图5.NCV7692负温度补偿工作电路图

 
图6.NCV7692短路检测电路图
 

图7.NCV7692 4或更多路的短路检测图

图8.NCV7692 短路保护图

图8.NCV7692 SmartFET控制电路图

图9.NCV7692刹车灯/尾灯应用电路图

图10.NCV7692大电流时刹车灯/尾灯应用电路图

图11.NCV7692没有微处理器的应用框图

评估板EVBUM2664

NCV7692 High-currentDaylight Running LightEvaluation Board

The evaluation board demonstrates high−current daylight running light (DRL) solution. The board regulates constant current of 0.54 A through two on−board white high power LEDs in the wide range of the supply voltage. The current is reduced for the board temperature above 85°C. The cooling is provided through passive heat sink mounted on the bottom side of the board. In case of LEDs short or opening, the current source is disabled and the fault may be detected by the ECU diagnostics.

评估板EVBUM2664主要特性:

• Wide range of supply voltage: 7 to 40 V (thermally limited)
• Two high−brightness on−board white LEDs
• Nominal LED current of 0.54 A
• Over−temperature current fold−back protection
• LED short−circuit and open−load emulation jumpers
• Positions for optional EMC capacitors
• One−side components assembly
• Passive cooling (heat sink)

图12.评估板EVBUM2664外形图

图13.评估板EVBUM2664大电流白天运行电路图

图14.NCV7692大电流DRL板外形图

图15.NCV7692一线驱动器车身电子控制单元(ECU)框图

图16.NCV7692 DRL EVB PCB设计图:左:顶层装配图;右:顶层综合图

图17.NCV7692 DRL EVB PCB设计图:顶层边视图

图18.NCV7692 DRL EVB PCB设计图:底层边视图

图19.NCV7692DRLV1GEVB评估板电路图