Two ways to protect switching power adapters?

During the development of new products for switching power adapters, in order to ensure that the adapter can adapt to the operating requirements of different environments during use and to provide users with continuous and stable current and voltage conversion, engineers usually provide appropriate output overload protection for the adapter. To ensure safe operation of the adapter. This article will introduce two widely used output overload protection technologies.

Constant power limit protection method

The constant input power limit protection method is one of the more common switching power adapter output protection technologies in the world. The protection principle of this method is to protect the circuit by limiting the maximum transmission power. But in a flyback converter, this technique can hardly protect the output components. For example, in a discontinuous flyback converter, the peak current of the primary side has been limited, that is, a limited transfer power is given. When the load resistance decreases and the load exceeds its limit value, the output voltage begins to decrease. Because of the product of the voltage and current of the specified input and the corresponding output, when the output voltage begins to fall, the output current will rise. During a short circuit, the secondary current will become very large and consume all the power in the switching power supply. This form of power limitation is generally only a supplement to certain limitations.

Flyback Overpower Limit Protection

Flyback overpower limit protection method is currently widely used in the development of adapters and manufacturers. This protection technology is an extension of the above form. In this form, there is a circuit to monitor the primary current and secondary voltage. Reduce power as output voltage decreases. In this way, when the load resistance decreases, the output current is reduced, and the secondary side components are prevented from being damaged by excessive stress. The disadvantage is that the lock-up phenomenon occurs when it is used in a non-linear load.