Self-protecting switch apparatus for controlling a heat element of a vehicle seat and a method for providing the apparatus

摘要

Current flow between a battery (14) and electrical ground (18) and through a load (16) is controlled by an apparatus (10). Preferably, the load (16) is a seat heat element. A current direction sensitive MOSFET (34) acts as a switch to control the current flow. The MOSFET (34) has a source (40) connected to the load (16), a drain (42) intended for connection to a positive terminal (26) of the battery (14), and a gate (46) for receiving a control voltage. Transistors (56, 66) control the voltage at the gate (46) of the MOSFET (34). The apparatus (10) is self-protecting against damage upon reverse polarity connection of the battery (14). A switch-protecting resistor (36) is intended for connection to electrical ground (18). The switch-protecting resistor (36) provides a path for electrical energy from the battery (14) to the gate (46) of the MOSFET (34) when the battery (14) is reverse polarity connected.