CXLE82137D is an LED constant current driver chip optimized for low power factor (PF) floating Buck topology. Its core advantages are "full-cycle current sampling" and "closed-loop control". Through real-time monitoring and adjustment of the average value of inductor current, it is within a very wide load voltage range (such as LED tri-proof light, line light and other multiple strings and applications) can still maintain high-precision output, effectively solving the current drift problem of traditional solutions when the load changes.
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[ CXLE82137D ]"
CXLE82137D full cycle sampling low PF floating ground Buck LED driver chip-JTM-IC high precision digital current adjustment scheme
In the fields of industrial lighting, outdoor lighting and high-demand commercial lighting, LED drive systems not only need high-precision stable output current, but also need to maintain stability within a wide load range and support safety, flexible output current regulation. JTM-IC (jtm-ic.com) launched CXLE82137D, it is the low PF floating Buck architecture LED constant current driver chip designed to meet this requirement. The chip usesFull-cycle closed-loop current sampling technology, achieving excellent load adjustment rate and high-precision constant current, and supportingDigital current adjustmentAndExternal NTC over-temperature protection, provides a complete and efficient solution for high reliability LED lighting system.
I. CXLE82137D Product Overview
CXLE82137D is an LED constant current driver chip optimized for low power factor (PF) floating Buck topology. Its core advantage lies inFull Cycle current sampling"AndClosed loop control", by monitoring and adjusting the average value of inductor current in real time, it can still maintain high-precision output in a very wide load voltage range (such as LED tri-proof light, Line light and many other strings and applications), it effectively solves the current drift problem of the traditional scheme when the load changes.
The chip supports digital current adjustment through external DIP resistor, and the current adjustment loop is separated from the power loop, which not only extends the service life of DIP switch, but also simplifies the PCB layout. At the same time, the chip integrates comprehensive protection functions and supports external NTC to realize temperature adjustable current reduction protection, greatly improving the reliability of the system in harsh environments such as high temperature.
II. Highlights of core technologies and functional advantages
2.1. Full-cycle closed-loop sampling and high-precision constant current
CXLE82137D sample the inductor current in each switching cycle and form a closed loop control through the internal error amplifier. Compared with the traditional peak current detection, this method can more truly reflect the average value of the output current, thus achieving excellent load adjustment rate when the load voltage changes greatly, and the constant current accuracy is as high as 3%.
2.2. Safe and flexible digital current adjustment function
The output current can be set in a wide range through the external DIP resistor of different resistance values on the CS pin. This design skillfully separates the current setting signal from the Power main circuit:
· Avoid large current flowing through DIP switchImproves the switch life and system reliability.
· Simplify PCB layout, shorter power routing, lower loss, and better EMI performance.
2.3. Double-track over-temperature protection mechanism
· Built-in over-temperature drop Current: When the chip junction temperature exceeds 145 ℃, the output current is automatically linearly reduced.
· External NTC over-temperature protection: through the external negative temperature coefficient thermistor of the NTC pin, the internal ambient temperature of the lamp or the temperature of the radiator can be detected in real time, and the current reduction or shutdown protection with adjustable temperature point can be realized, which perfectly adapts to the heat dissipation design of different lamps.
2.4. Comprehensive protection functions
·VCC undervoltage lockout
· Cycle-By-Cycle throttling protection
· Output open circuit/overvoltage protection
· Output short circuit protection
· FB anti-interference OVP protection
2.5. Optimized EMC and working mode
The chip works in critical conduction and Frequency Limiting mode, which effectively optimizes electromagnetic compatibility and simplifies the design difficulty of system EMI.
III. Internal structure and working principle
CXLE82137D internal integration of error amplifier, logic control, drive circuit, demagnetization detection, leading edge blanking, precision current sampling reference and multiple protection modules.
Startup Process: After the system is powered on, the input voltage charges the VCC capacitor through the startup resistor. When the VCC voltage reaches the turn-on threshold (typical value 15V), the internal control circuit of the chip starts to work. The voltage of the COMP pin is quickly established, and the chip starts to output the driving pulse.
Constant current control mechanism: the chip samples the inductor current through the CS pin resistor and compares it with the internal high-precision reference voltage VREF (typical value 200mV). After the error amplifier and compensation network are adjusted, the GATE output is controlled, achieve accurate constant current control. The output current calculation formula is as follows:
IV. Key design guidelines and parameter settings
4.1. Output current setting
The output current is mainly determined by the CS sampling resistor RCS:
By changing the DIP resistor network connected to the CS pin, the internal reference can be adjusted to realize current programming.
4.2. External NTC network configuration
The NTC pin can connect thermistor to the voltage dividing network of the fixed resistor. When the voltage of the NTC pin is lower than that of the VNTC (typical value is 0.3V), the external over-temperature and down-current function starts. Through reasonable selection, the temperature point of reducing current can be matched with the heat dissipation characteristics of specific lamps.
4.3. Feedback resistance and OVP settings
FB pin is used for demagnetization detection and output overvoltage protection. Its divider resistance network needs to meet:
The typical value of VFB_OVP is 2.025V. The divider resistance must be placed near the FB pin, and it is recommended to add a small capacitor between FB and GND to filter out noise.
V. PCB layout and EMI optimization suggestions
5.1 VCC bypass capacitor: must be close to the VCC and GND pins of the chip.
5.2 Current sampling loop: The Power ground wire of the CS sampling resistor should be short and thick, and be connected to the GND pin of the chip separately, and be routed separately from the signal ground to ensure the sampling accuracy.
5.3 Power loop minimization: Make sure to reduce the Loop area formed by the input capacitor-power tube-inductance and the inductance-flyback diode-output capacitor, which is the key to reduce radiation EMI.
5.4 FB and NTC pin layout:
·FB divider resistance must be close to the FB pin, and its nodes should be far away from high-frequency noise sources.
·We recommend that you place filter capacitor between the NTC pin and GND to prevent false triggering of switching noise.
6. Typical application scenarios
CXLE82137D with its high precision, wide load adaptability and powerful protection functions, it is very suitable for application in:
·LED tri-proof light(Dustproof, waterproof, anti-corrosion): suitable for factories, warehouses, parking lots and other environments.
·LED Line light: it is often used for commercial lighting and building outline lighting, and requires good load adjustment rate for driving.
·Other industrial and outdoor LED lamp requiring high precision dimming and high reliability.
VII. Packaging and ordering information
CXLE82137D adopts the industry standard SOP-8 package, with small size and good heat dissipation performance, which is convenient for automatic patch production. The order model is CXLE82137D, and the package is in the form of a reel, 4000 pieces per plate.
VIII,Related productsmore...
IX. Conclusion
CXLE82137D through the innovative full-cycle closed-loop sampling technology, the constant current accuracy problem in wide-load LED applications has been successfully solved. Its unique digital current adjustment interface, internal and external dual over-temperature protection and comprehensive system protection functions together constitute a highly reliable, highly flexible and easy-to-design LED Drive solution.
JTM-IC has always been focusing on providing leading power management chips for the market, helping the LED lighting industry to move towards high efficiency, intelligence and reliability with technological innovation. For detailed technical documents, reference designs, or application samples of CXLE82137D, please visit the official website of JTM-IC:jtm-ic.com, our technical team will provide you with professional support.
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