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CXAC85254: current mode PWM controller of innovative high-power power supply designfbF嘉泰姆

In the fields of LED display screen, battery charging system and industrial power supply, efficient and stable power management scheme is very important. CXAC85254, as a cost-effective current mode PWM controller, solves the key pain points of medium and high power flyback/forward power supply through innovative design. This article will deeply analyze its core technical characteristics and industry application schemes.fbF嘉泰姆

I. Breakthrough technical characteristics

1. Dual optimization of EMI and energy efficiencyfbF嘉泰姆

a. Built-in TikTok function: ± 4% frequency jitter range effectively disperses EMI noise and simplifies filtering designfbF嘉泰姆

B. Green energy saving mode: automatically switch 21kHz hiccup mode when light load/no load, reducing switching loss by 60%fbF嘉泰姆

c. Only 2.3mA work Current: with 6μA ultra-low starting current, the standby power consumption is significantly reduced.fbF嘉泰姆

2. Triple protection systemfbF嘉泰姆

3. Flexible frequency configurationfbF嘉泰姆

The PWM frequency can be accurately set through the external resistor of RI pin:fbF嘉泰姆
Fosc(KHz) = 3640 / Ri(KΩ)fbF嘉泰姆
Typical 56 Kohm resistance corresponds to 65kHz switching frequency, perfectly balancing efficiency and noise.fbF嘉泰姆

II. Industry application plan

1. Lithium battery charging systemfbF嘉泰姆

a. Use CXBD73136 to achieve constant voltage and constant current controlfbF嘉泰姆

B. BO pin implements input undervoltage lockout (UVLO) to avoid battery overdischargefbF嘉泰姆

c. Accurate adjustable temperature protection threshold: RT pin voltage ≤ 1v trigger shutdownfbF嘉泰姆

2. Industrial Power Supply DesignfbF嘉泰姆

| Parameters | CXAC85254 | Regular controller |
| --------------- | ----------- | ------------ |
| Maximum duty cycle | 50% | 45% |
| Drive capability | 20mA | 10mA |
| Response speed | 130ns rise | >200ns |

3. Motor drive power supplyfbF嘉泰姆

a. Slope compensation function to suppress subharmonic oscillationfbF嘉泰姆

B. CS pin leading edge blanking (250ns) effectively filters out switch spikesfbF嘉泰姆

c. Overload protection delay 55ms to avoid false triggeringfbF嘉泰姆

III. Analysis of key protection mechanisms

1. Temperature protectionfbF嘉泰姆

Build real-time monitoring through external NTC resistor:fbF嘉泰姆
Vrt = I _rt × Rntc(I _rt=75μA)fbF嘉泰姆
When the voltage of RT pin ≤ 1V, the protection is triggered, and> 1.1V is automatically recovered with an error of ± 0.05V.fbF嘉泰姆

2. Intelligent fault managementfbF嘉泰姆

a.VCC overvoltage protection: 28.2V ± 1V action thresholdfbF嘉泰姆

B. Optocoupler open circuit protection: FB pin voltage> 5.3v trigger safety shutdownfbF嘉泰姆

c. Power Tube protection: Built-in LEB 120ns overcurrent detection delayfbF嘉泰姆

IV. Measurement of design advantages

1. Energy efficiency improvement planfbF嘉泰姆

a. Use SOP8/DIP8 package to optimize heat dissipation (thermal resistance & theta;JA only 80℃/W)fbF嘉泰姆

B. The driving capability is 20mA, which supports fast switching (Tr = 130ns/Tf = 50ns)fbF嘉泰姆

c.50% Maximum duty cycle improves transformer utilizationfbF嘉泰姆

2.EMC design simplificationfbF嘉泰姆

| Test items | No TikTok | Enable TikTok |
| ------------- | -------- | ----------- |
| 30MHz radiation | -5dB | -12dB |
| Conducted noise | Excessive | Pass |

V. Typical application circuit

1. Double-tube forward topologyfbF嘉泰姆

With CXBD3531 MOSFETs, it can realize 200W industrial power supply:fbF嘉泰姆

a.BO pin detects bus voltagefbF嘉泰姆

B. RI set 65kHz operating frequencyfbF嘉泰姆

c.RT external 100K NTC to achieve 85 ℃ protection pointfbF嘉泰姆

2. Key points of charger designfbF嘉泰姆

a. Configure 4.6V overload threshold for FB pinfbF嘉泰姆

B. CS resistance formula:Rcs = 0.88V / IpkfbF嘉泰姆

c. Optimize the feedback loop with FB short circuit current (1.2mA)fbF嘉泰姆

Conclusion

CXAC85254 has become an ideal choice for charging equipment, industrial power supply and LED Drive system due to its 50% high duty cycle, accurate temperature protection and EMI optimization characteristics. The cooperative design of 3.5mA low operating current and multiple protection mechanisms significantly improves the system reliability. With the increasingly strict energy conservation regulations, the Green mode control technology of the chip will provide core support for the new generation of power supply solutions.fbF嘉泰姆

For detailed PDF specifications, please scan WeChat and contact us. You can also get free samples and technical support.!fbF嘉泰姆

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   Product packaging diagram fbF嘉泰姆

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   Circuit Schematic diagram fbF嘉泰姆

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  Relevant chip selection guide            More similar products.....fbF嘉泰姆

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