Hello everyone, I have a switching power supply chip with UC3845, fault: turn on the power instantaneous power indicator light and then off. After the investigation did not find a short circuit phenomenon. When the shortcomings of several consecutive shortcuts on the receiving side of the two pins, the power can be activated. What is the reason for this? thank you all!
The mains voltage is unstable or the quality of the plug or the power outlet is poor and the contact is bad.
Mains voltage instability solution: For the frequent power supply instability in the region, we can buy ups power supply or 130-260v wide switching power supply to ensure the stability of the computer work.
The quality of the plug or the power outlet is poor and the contact is bad. Solution:
① do not plan to save money and buy cheap power plug, buy some brand-name power plug, because it is automatically installed within the machine crimping, no manual welding.
② whether it belongs to the wall socket internal virtual connection, we can change the host for a wall outlet try to see if there is the same automatic restart problem.
In addition, increase the output capacitor, will only increase the impact of the starting current, no way to start. Reduce the voltage is not feasible, because it would lose their own meaning, and for a large switching power supply that can be considered a problem, wasted. Analysis of the actual current detection link and peak and power limit links, because they do not know what specific program, so do not know, the appropriate tune can be a little bit.
Oh, the above two answers I think can not help you solve the problem, because it is not feasible. First of all, according to what you say, you can accurately judge, you are full or overloaded when the normal start. This only shows a reason that the power is instantly activated when the impact is protected. The solution to the problem is to analyze the cause of the problem first. Where the protection is due to power on the moment when the load with the impact of over-current. So the overcurrent protection value should be slightly adjustable to solve. Such as single-ended flyback power supply, can reduce the resistance of the lower end of the MOS tube in order to increase the output over-current protection value, half-bridge or full-bridge circuit, then appropriate to reduce the peak current protection value or output over-current protection value, solved. Many of the output overcurrent or short circuit protection is used in the transformer primary side using the transformer (magnetic or magnetic core) to detect the transformer primary current, to protect the output overload situation. The value of this detected can be appropriately adjusted (the voltage drop resistance value can be appropriately reduced).
