Working Principle of Overcurrent Protection in Linear Adapters

　　The overcurrent protection mechanism in linear adapters is designed to prevent damage to the adapter and the connected device when an excessive current flows. A common method is to use a current - sensing resistor. This resistor is placed in series with the output path of the adapter. As current flows through the resistor, a voltage drop is generated across it according to Ohm's law (V = IR).

　　This voltage drop is then monitored by a circuit, often an operational amplifier (op - amp) configured as a comparator. The comparator compares the voltage across the current - sensing resistor with a pre - set reference voltage. When the current exceeds the rated value, the voltage drop across the current - sensing resistor becomes large enough to exceed the reference voltage. At this point, the comparator output changes state, triggering a protection action.

　　Typically, this action involves turning off a power switch, such as a MOSFET, to interrupt the current flow. Some overcurrent protection circuits also incorporate a time - delay feature. This is to prevent false triggering due to momentary current surges, such as inrush currents when a device is first powered on. The time - delay allows the circuit to distinguish between normal transient currents and true overcurrent conditions. Once the overcurrent condition is resolved, the protection circuit can be reset, either manually or automatically, to resume normal operation of the adapter.

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