Shenzhen Xinshunxiang Technology Co., Ltd. Contact: Nie Zhihui 13632552696 WeChat: 13632552696

Overview:

PT4421 is an LED current ripple elimination control chip, which is mainly used to cooperate with active power factor correction LED drivers to eliminate low frequency ripple of single-stage APFC output current and low frequency flicker of LED lights.

PT4421 adopts a patented high-efficiency drive mechanism, which can automatically adapt to different LED output voltages and currents, eliminate LED current ripple, and ensure the lowest loss of power MOS tubes.

PT4421 has over temperature protection and VCC under voltage protection function.

The PT4421 is packaged in SOT23-6.

Features:

? Adaptive Ripple Current Cancellation Controller

? Simple peripheral components

? Wide range of LED voltages

? Wide range of LED current

? Chip power supply under-voltage protection

? Chip over temperature protection function

? SOT23-6 package

application:

? LED fluorescent lamp

? LED bulb/spotlight

? LED ceiling light

? Other LED lighting products

Function description

PT4421 is an LED current ripple elimination control chip, which is mainly used to cooperate with active power factor correction LED drivers to eliminate output current low frequency ripple and LED stroboscopic.

working principle

The drain of the external MOSFET is connected to the cathode of the LED to control the LED current, the detection resistor Rcs is connected between the source of the MOSFET and GND, and the gate of the MOSFET is connected to the DRV port of the PT4421.

The PT4421 drives the MOSFET, converts the ripple current of the LED into the ripple voltage on the MOSFET, and ensures that the voltage across the LED is constant to keep the current on the LED constant.

start up

The working voltage of PT4421 is provided by the bus voltage after charging the VCC capacitor through the start-up resistor. When the VCC voltage rises to the threshold start-up voltage, the chip starts to work.

Starting resistance calculation method:

RST ? (VLED ? 15V) *_1000

(Ω)

The starting resistance needs to be adjusted according to the output load voltage, and the minimum output voltage should be used to calculate the starting resistance value.

RCS resistor setting RCS has a limit voltage of 0.3V, the maximum output current will be limited to 0.3V/Rcs, which can support hot-plugging and short-circuit protection of output LEDs.

protect. Calculation method of sampling resistance during normal operation: OUTCS I0.1V R ? Among them, IOUT is the average value of the output current of the front-end system.

PT4421 will adaptively adjust the LED current, so that the LED current is equal to the average value of the input current, and the accuracy of the sampling resistor is not high. The input capacitor selection system needs an input capacitor with sufficient value to store the energy of the input current ripple. The larger the input capacitor, the smaller the system loss. It is recommended to select the input capacitor CIN ? 1 ? ILED(mA)uF