Circuit Power Supply

The circuit is based on IC1, an LTC1430 PWM controller. The current-limiting feature of the IC operates by sensing the voltage across the high-side MOSFET and compares it with a threshold voltage developed across R3.

Source: http://www.edn.com/article/CA46728.html

The three major types of current-limit-protection mechanisms are constant, foldback, and hiccup. Hiccup current limit performs the best of the three types; however, the implementation is rather complex. In this scheme, upon detection of an overcurrent event, the whole power supply shuts down for an interval before it tries to power itself up again. The cycle repeats until the overcurrent fault disappears.

Source: http://www.edn.com/article/CA305485.html

Although this short-circuit protection is often sufficient, some applications require a true current limit, such as the implementation in Figure 1’s circuit. A low-value resistor, R1, performs current sensing. The circuit applies the voltage across this resistor, through R2 and R3, to the inputs of the comparator IC2A. R4 and R8 create initial offset voltages to set the current-limit trip point.

Source : http://www.edn.com/archives/1998/052198/11di.htm