Two ways to protect the switching power adapter

Issue Time:2006-12-04
In 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 provide users with continuous and stable current-voltage conversion work, engineers usually provide appropriate output overload protection for the adapter. To ensure the safe operation of the adapter. This article will introduce you to two widely used output overload protection technologies to help engineers better complete the design of new adapter products.

Constant power limit protection
The constant input power limit protection method is one of the most common output protection technologies for switching power supply adapters in the world. The protection principle of this method is to protect the primary side circuit by limiting the maximum transmission power. However, in a flyback converter, this technique hardly protects the secondary output components. For example, in a discontinuous flyback converter, the primary peak current has been limited, that is, the limited transmitted power is given. When the load resistance decreases and the load exceeds its limit, the output voltage begins to drop.

It is precisely because of the voltage and current products of the specified input and the corresponding output that the output current will rise when the output voltage begins to drop. In the event of a short circuit, the secondary current will become very large, consuming all of the power in the switching power supply. This form of power limitation is generally only used as a supplement to certain limitations, such as secondary side current limiting, which is a complementary limitation of the circuit.

Flyback super power limit protection
The counter-attack ultra-power protection method is currently widely used in domestic adapter development and manufacturer production processes. This protection technology is an extension of the upper speed form. In this form, there is a circuit to monitor the primary current and the secondary voltage. , reducing power when the output voltage is reduced. In this way, the output current is reduced when the load resistance is lowered, and the secondary component is prevented from being subjected to excessive stress damage. The disadvantage is that the locking phenomenon occurs when used for a non-linear load.

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