Flexible fault protection

Many applications require the capability to automatically disconnect power from an operating circuit. Such applications include thermal shutdown of high-voltage power supplies in radar and X-ray systems, shutdown to limit inrush current during power-up or hot-swapping of pc cards, and shutdown to ensure that a card is properly seated before power is applied. In general, a power fault system will keep the power off following the system fault, until it is deliberately reset.

Figure 1 is a flexible circuit that limits current or removes power in response to a command from the user or other fault-indicating signal. It accommodates manual-reset (MR), over-temperature, and interlock-switch inputs. U1, for instance, is a circuit-breaker IC designed to offer protection in hot-swap applications. Residing on either the backplane/host side or the removable-card/remote-device side of the backplane connectors, it guards against start-up faults when a card or board is inserted into a rack or host with the main power supply turned on.

Figure 1. This circuit provides general over-current and over-temperature protection.