淺談On Semi NCV7692汽車LED燈電流控制的解刨

On Semi公司的NCV7692汽車LED燈電流控制器,采用外接NPN雙極器件和反饋電阻來調整驅動LED的電流.單個驅動器使用戶能靈活增加單路到多路系統中.專用的調光特性通過PWM輸入引腳來實現.當檢測到開路或短路時單路驅動器就開關斷.LED亮度采用串聯在雙極晶體管的外接電阻進行編程.單個NCV7692可驅動多個LED串.NCV7692可采用PWM控制,外接可編電流電阻,可選擇負溫度系統電流控制,開路LED串和短路LED串診斷,多個LED串控制,滿足AEC?Q100 規范和PPAP功能.主要用在汽車后組合燈(RCL),日間燈(DRL),霧燈,中央高位剎車燈(CHMSL)陣列,轉向燈和其它外部調制應用,通用汽車線性電流LED驅動器.本文介紹了NCV7692主要特性,框圖和多種應用框圖,以及評估板EVBUM2664主要特性,電路圖和評估板EVBUM2664應用電路與PCB設計圖.

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應用:

? 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

圖1.NCV7692框圖

圖2.NCV7692應用框圖

圖3.NCV7692微處理器控制應用框圖

圖4.NCV7692輸出驅動配置圖

圖5.NCV7692負溫度補償工作電路圖

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圖6.NCV7692短路檢測電路圖
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圖7.NCV7692 4或更多路的短路檢測圖

圖8.NCV7692 短路保護圖

圖8.NCV7692 SmartFET控制電路圖

圖9.NCV7692剎車燈/尾燈應用電路圖

圖10.NCV7692大電流時剎車燈/尾燈應用電路圖

圖11.NCV7692沒有微處理器的應用框圖

評估板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.

評估板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)

圖12.評估板EVBUM2664外形圖