Electronic Components Datasheet Search |
|
WS3440 Datasheet(PDF) 5 Page - Shenzhen Winsemi Microelectronics Co., Ltd |
|
WS3440 Datasheet(HTML) 5 Page - Shenzhen Winsemi Microelectronics Co., Ltd |
5 / 8 page Copyright@Winsemi Microelectronics Co., Ltd., All right reserved. W/T-Y027-Rev.A/1 May.2014 WS3440 Product Description WIN SEM I M ICROELECTRON ICS WIN SEM I M ICROELECTRON ICS WIN SEM I M ICROELECTRON ICS WIN SEM I M ICROELECTRON ICS WIN SEM I M ICROELECTRON ICS 0813 F F F Function unction unction unction Description Description Description Description WS3440 is a constant current controller, designed for driving non-isolated buck LED power supply. WS3440 uses patent constant current control method and source driver structure, excellent constant current characteristic is achieved with low counts components. Low cost and high efficiency of system is realized. Start Start Start Start up up up up The Vcc will be charged through the startup resistor when the system is powered on. When the voltage on Vcc reaches the startup voltage threshold, the controller starts to switching. The Vcc voltage of WS3440 is clamped to 7.3V by internal Zener diode. Constant Constant Constant Constant Current Current Current Current Control Control Control Control and and and and Output Output Output Output Current Current Current Current Setting Setting Setting Setting The WS3440 uses patent constant current control method, excellent constant current is achieved with low counts components. The WS3440 senses the peak current in inductor cycle by cycle. The CS Pin is connected to the input of internal current comparator, and compared with the internal 400mV reference voltage. The external power MOSFET will be turned off when the CS pin voltage reaches the voltage threshold. The comparator has a 350ns LEB timer to avoid mis-trigger. The peak current in the inductor is given by: ) ( 400 mA R I CS PK = The Rcs is the resistance of current sense resistor The current in LED can be calculated by the following equation: 2 PK LED I I = The IPK is the peak current in inductor Source Source Source Source Driver Driver Driver Driver Structure Structure Structure Structure The WS3440 uses the patent source driver structure. The typical operation current is as low as 200uA, the auxiliary winding is not need. So the system design is simple and the cost is low. Inductance Inductance Inductance Inductance Calculation Calculation Calculation Calculation The WS3440 is designed to work in inductor current critical mode; the energy will be stored in the inductor when the MOSFET is turned on. The turn on time is given by: LED IN PK on V V I L t − × = The L is the inductance. The Ipk is the peak current in inductor. The VIN is the input rectified voltage. The VLED is the voltage on LED. When the power MOSFET is turned off, the inductor current will decrease from the peak current to zero. The turn off time is given by: LED PK off V I L t × = The MOSFET will be turned on again when it detects the inductor current goes to zero. The inductance can be calculated by the following equation: IN PK LED IN LED V I f V V V L × × − × = ) ( The f is the system switching frequency, which is proportional to the input voltage. So the minimum switching frequency is set at lowest input voltage, and maximum switching frequency is set at highest input voltage. The WS3440 internally set the minimum off time to 4us and maximum off time to 240 us. When the inductance is very small, the toff may goes below the minimum off time and the inductor current becomes discontinuous. So the output LED current will be smaller than the setting value. If the inductance is too large, the toff may goes beyond the maximum off time and the inductor current becomes continuous. And the output LED current will be larger than the setting value. So it’s very important to select a right inductance. The WS3440 also internally set the maximum on time to 40us. When the input voltage is very low or LED output |
Similar Part No. - WS3440 |
|
Similar Description - WS3440 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |