currentlimit

Current limit is the maximum electrical current that a device, circuit, or system is designed to permit. It serves to protect components from damage due to overcurrent, short circuits, or excessive load, and to regulate the behavior of power converters and drivers.

In power supplies, motor controllers, and LED drivers, current limit can be implemented as a hard clamp or as a foldback that reduces current when the limit is reached. A hard limit maintains the set current value, potentially causing a drop in voltage, while foldback lowers current to a safer level to minimize thermal stress.

Most implementations use a current sense element, such as a shunt resistor or Hall sensor, together with a sensing amplifier and a comparator or control loop. When the sensed current exceeds the threshold, the controller reduces the output by adjusting duty cycle, output impedance, or a transistor gate, thereby preventing damage. Some devices latch off when the limit is tripped and require a reset to resume operation.

Current limit is specified in device datasheets as a current value, with information on accuracy and temperature dependence. It is common in linear regulators, switching regulators, motor drivers, battery chargers, and LED drivers. The limit can interact with other protections, such as overvoltage or thermal shutoff; in some cases, protection systems work cooperatively to protect both load and source.

Design considerations include selecting an appropriate sense resistor to balance power loss and accuracy, ensuring stable control without oscillations, and testing across temperature and supply variations to verify reliable limiting.