| In the field of architectural lighting, landscape lighting and display screen, LED arrays become the source. This paper design chips to drive and protect the LED arrays, including constant current driver chip and LED open circuit protection chip.Constant current driver chip adopts a kind of negative feedback mechanism. The chip compares the sense voltage with the internal reference voltage to adjust the resistance of bipolar transistor. The both ends voltage of the LED and current will maintain stable. The driver chip has three pins. The usage of chip is connecting the control pin to output pin with a resistance. The input pin connects the LED in series with the power. The working voltage range is from 3 V to 42 V, maximum output current is 850 mA, current precision is ±5%.The user can change the output current by adjusting the sampling resistance.Constant current driver chip is made up of the following blocks, the power block which supplies power for the inside circuits; the reference block which provides reference voltage and current; sampling and compare block which compares the external voltage with reference voltage to drive the power transistor; the power transistor block which drives the LEDs; the protection block.The protect chip adopts diode chain structure, including multiple series of diodes and a reverse parallel diode. The usage of the chip is connected both ends of a LED in parallel. When LEDs work normally, the diode chain remains shut-off for the high threshold voltage. When a LED is off, the chip is turned on because of the rising voltage and it can ensure that other LEDs work normally. The reverse diode in parallel is used for LED ESD protection. At the same time, this paper puts forward a feasible way for manufacture of diode chain.The chips are designed and verified by cadence software under 1μm 40 V BCD process. Finally, parameter testing and function verification are carried out on the actual circuit, and the desired design goal is achieved. |
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