Four ways to protect the switching power adapter

Method 1, pulse-by-pulse super power or over current limit

Over-power or over-current limiting on pulse-by-pulse is a very effective output overload protection method in practical applications, and is often used in additional secondary-side current limiting protection. In previous switching devices, the input current was monitored in real time. If this current exceeds the specified limit current value, the turn-on pulse is terminated. In a non-continuation flyback converter, the maximum current determines the power of the circuit. This type of protection circuit becomes a real power limit protection circuit.

     Method 2, super power delay shutdown protection

The ultra-power delay shutdown protection is an output overload protection technology that must be provided during the development of the power adapter. In a time-delayed trip system, short-term transient current requirements are tolerated, and the power supply is turned off only when the current stress exceeds a safe value for a long time. The provision of short transient currents will not compromise the reliability of the power supply and will not have a significant impact on the cost of the power supply. Only long-term continuous current requirements will affect the cost and size of the circuit.

    Method three, flyback ultra power limit protection method

The counter-attack ultra-power protection method is currently widely used in domestic adapter development and factory 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.

    Method four, constant power limit protection method

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.