CXAC85269 is a highly integrated and high-performance current mode PWM control chip designed specifically for flyback converters. It has low standby power consumption (typical value below 100mW) and high conversion efficiency, automatically entering the "jump cycle mode" under no-load or light load conditions, effectively reducing switch losses and improving system energy efficiency. The chip integrates multiple protection functions, including cycle by cycle current limiting (OCP), overload protection (OLP), VDD undervoltage lockout (UVLO), over temperature protection (OTP), and adjustable overvoltage protection (OVP), ensuring the safe and reliable operation of the system in various abnormal situations.
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[ CXAC85269 ]"
CXAC85269 flyback PWM control chip: high-performance and low-power power management solution
In today's power management chip market, high efficiency, low power consumption, and high integration have become the core demands of product design. CXAC85269, as a current mode PWM control chip optimized for flyback converters, is widely used in various AC/DC adapters and switching power supply systems due to its outstanding performance, comprehensive protection mechanism, and excellent cost control capability. This article will provide an in-depth analysis of the technical features, functional structure, working modes, and typical applications of CXAC85269, to assist engineers in achieving more efficient and reliable power design.
1、 Chip Overview and Core Advantages
CXAC85269 is a highly integrated and high-performance current mode PWM control chip designed specifically for flyback converters. It has low standby power consumption (typical value below 100mW) and high conversion efficiency, and automatically enters the“ mode under no-load or light load conditions; Jump cycle mode; Effectively reduce switch losses and improve system energy efficiency. The chip integrates multiple protection functions, including cycle by cycle current limiting (OCP), overload protection (OLP), VDD undervoltage lockout (UVLO), over temperature protection (OTP), and adjustable overvoltage protection (OVP), ensuring the safe and reliable operation of the system in various abnormal situations.
In addition, the chip also has frequency jitter function, effectively improving the EMI performance of the system and eliminating audio noise interference below 20kHz that may occur during operation, enhancing the user experience.
2、 Main functional features
2.1. High efficiency and low-power design
• 65kHz fixed switching frequencyOptimize system efficiency and size within a reasonable range.
• Jump cycle modeAutomatically reduce the switching frequency under light or no-load conditions, significantly reducing standby power consumption.
• Soft start functionReduce the current surge during the startup process and lower the electrical stress on the power MOSFET.
2.2. Comprehensive protection mechanism
• Adjustable Overvoltage Protection (OVP)Support external Zener diode regulation, flexibly adapting to different application scenarios.
• Cycle by cycle current limitation (OCP)Ensure constant output power across the entire voltage range.
• Overload protection (OLP) and over temperature protection (OTP)Equipped with automatic recovery function to enhance system reliability.
• VDD undervoltage lockout (UVLO) and overvoltage protectionEquipped with hysteresis function to prevent accidental triggering.
2.3. Excellent EMI and noise control
• frequency jitterDisperse harmonic energy, reduce system EMI interference, and simplify filtering design.
• Audio noise cancellationBy optimizing the modulation method, noise within the audible frequency range can be avoided.
2.4. Packaging and Pin Design
The chip adopts SOT23-6 packaging, with a compact structure, suitable for space limited application scenarios. The functions of each pin are as follows:
• ANDFunction configuration pins
• FBFeedback input terminal, used for output voltage sampling
• RTExternal timing resistor, set operating frequency
• SENSECurrent detection input terminal, supporting leading edge blanking function
3、 Typical application scenarios
CXAC85269 is suitable for various AC/DC flyback converter systems, including but not limited to:
• AC/DC adapterSuch as laptop power supplies, mobile phone chargers, etc
• Netbook and tablet charger
• Set top box power module
• Open switch mode power supply (SMPS)
Its high integration and comprehensive protection functions make it an ideal choice for various consumer electronics and industrial power supply designs.
4、 System working principle and design points
4.1. Startup and working mode
After the system is powered on, the VDD capacitor charges to the startup threshold and the chip starts working. Under normal operating conditions, the chip performs PWM modulation at a frequency of 65kHz. When the load decreases, the system automatically switches to the skip cycle mode, reducing the number of switches and minimizing losses.
4.2. Frequency jitter and EMI optimization
The chip integrates a frequency jitter module internally, which disperses harmonic energy over a wide frequency band by slightly modulating the switching frequency, thereby reducing conducted and radiated EMI levels and helping the system easily pass EMC certification.
4.3. Detailed explanation of protection mechanism
• OVP protectionThe protection threshold can be set through an external Zener diode to adapt to different output voltage requirements.
• OCP and OLPDetect current cycle by cycle, and immediately limit output power when overcurrent or overload is detected.
• OTP and UVLOWhen the chip temperature exceeds the set value or the VDD voltage is abnormal, the system enters a protective state and automatically recovers.
4.4. PCB design suggestions
• The VDD bypass capacitor should be arranged closely to the chip pins to ensure stable power supply.
• The current detection path should be short and direct to avoid noise interference.
• The power ground and signal ground should be arranged separately, with a final single point grounding to reduce common mode interference.
V. Summary
CXAC85269 is a high-performance, low-power current mode PWM control chip that integrates advanced control logic and comprehensive protection functions, suitable for various flyback power systems. Its excellent skip cycle control, frequency jitter technology, and automatic recovery protection mechanism make it outstanding in improving system efficiency, reducing standby power consumption, and enhancing reliability.
CXAC85269 can provide stable and efficient power management solutions for open switch power applications such as mobile phone chargers, laptop adapters, and set-top box power supplies, helping customers shorten development cycles and reduce system costs.
If you need to obtain CXAC85269 samples, technical information, or apply for technical support, please visitJTM-IC official websiteWe are committed to providing customers with high-quality integrated circuit products and professional technical services, helping your products stand out in the global market.
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