Datasheet > A9912

A9912

更新时间： 2022-02-26 12:26:32

品牌	Logo	应用领域
创瑞 - AITSEMI		驱动输入元件
页数	文件大小	规格书
10页	248K
描述
85~265V AC INPUT LED CONSTANT CURRENT DRIVER

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A9912 数据手册

A9912

AiT Semiconductor Inc.

AC-DC LED DRIVER

www.ait-ic.com

85~265V AC INPUT LED CONSTANT CURRENT DRIVER

DETAILED INFORMATION

Application Information

The A9912 is optimized to drive buck LED drivers using open-loop peak current mode control. This method of

control enables fairly accurate LED current control without the need for high side current sensing or the

design of any closed loop controllers. The IC uses very few external components and enables both Linear and

PWM dimming of the LED current.

A capacitor connected to the T_OFFpin programs the off-time. The oscillator produces pulses at regular

intervals. These pulses set the SR flip-flop in the A9912 which causes the GATE driver to turn on. When the

FET turns on, the current through the inductor starts ramping up. This current flows through the external

sense resistor RCS and produces a ramp voltage at the CS pin. The comparators are constantly comparing

the CS pin voltage to both the voltage at the LD pin and the internal 200mV. Once the blanking timer is

complete, the output of these comparators is allowed to reset the flip flop. When the output of either one of the

two comparators goes high, the flip flop is reset and the GATE output goes low. The GATE goes low until the

SR flip flop is set by the oscillator. Assuming a 30% ripple in the inductor, the current sense resistor RCS can

be set using:

Note：（1） L₁is the value of the inductance.

（2） V_LEDis the sum of all the series of LED voltage

A constant off-time peak current control scheme can easily operate at duty cycles greater than 0.5 and also

gives inherent input voltage rejection making the LED current almost insensitive to input voltage variations.

฀

Input Voltage Regulator

When a voltage is applied at the decent resistor, the A9912 maintains a constant 6.5V at the V_INpin. This

voltage is used to power the IC and any external resistor dividers needed to control the IC. The V_INpin must

be bypassed by a low ESR capacitor to provide a low impedance path for the high frequency current of the

output GATE driver.

REV1.1

- OCT 2013 RELEASED, MAY 2015 REVISED -

- 5 -

1 2 3 456 7 8...10

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型号	品牌	描述	获取价格	数据表
A9912M8R	AITSEMI	85~265V AC INPUT LED CONSTANT CURRENT DRIVER	获取价格
A9912M8VR	AITSEMI	85~265V AC INPUT LED CONSTANT CURRENT DRIVER	获取价格
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