Abstract: A thermal overload protection circuit and method for protecting switching power amplifier circuits provides protection against latch-up and other failures due to energy returned from an inductive load when the amplifier output is disabled in response to a thermal overload condition. Upon detection of a thermal overload condition, rather than immediately disabling the switching power output stage, the switching power output stage is driven toward a fifty-percent duty cycle of operation for a predetermined time period so that energy stored in inductance of the load is reduced, preventing back-currents that would otherwise may cause latch-up within the integrated circuit when the switching power output stage is disabled. After the time period has elapsed, the switching power output stage is disabled. Alternatively, the current through the inductive load is measured and the switching power stage is disabled after the magnitude of the current has fallen below a threshold.

Abstract: Methods, systems, and apparatuses of this invention provide lightweight, economical, safe and adaptable means or retrieving an individual from a confined or an enclosed space, such as a storage vessel, storage tank, cargo transport tank, or any other enclosed container.