Temperature controlled fan---DC regulated power supply

Brief introduction of temperature control fan module
       》This power supply was bought from a small yellow croaker for 280 meters. When I just powered on the machine, I heard the roar of the fan at full power, which was really unbearable, so I spent some time and effort to make this module.
       》》》Disassembly will damage the warranty sticker, so friends who need it, please consider carefully before doing it
       》》》Because it may come into contact with the mains, please completely cut off the power during disassembly and installation to ensure personal safety.
Related video: UTP3315TFL-II DC regulated power supply-modify temperature control fan (completed)_哔哩哔哩_bilibili
1. Temperature control principle
       A, PWM control
       B, series temperature control resistor
       C, adjust fan voltage
       Solution A: This solution was originally considered feasible. After testing, it was found that the fan could not be started at low duty cycle. Whether the frequency was 2K or 100Hz, it could not complete the adjustment of 0 to 100% duty cycle well, so this solution was abandoned.
       Solution B: It’s meaningless, give up.
       Solution C: High playability and scalability, voltage regulation can also meet the speed regulation requirements, so it is the right choice. (Disadvantages: high cost)
 
1. Heat point
        The heat of this power supply is mainly concentrated in the heat sink and the rectifier bridge of the control board. The measured 30V/5A output, after running for 3 or 4 minutes, the rectifier bridge reached about 150 degrees Celsius, so this is why I also added a 12V fan to blow air on the rectifier bridge.
 
2. Module resources
         7V~24V input, two-way NTC detection, a set of serial communication, a set of I2C ports (unused), two sets of fan power output (parallel mode), a set of 5V output
       board frame: 50mm*41mm
 
3. Voltage regulation principle
          The buck IC is used to step down the 24V to supply the fan, and the digital potentiometer is used to adjust the low-side resistance of the buck IC feedback to achieve digital control voltage regulation.