Auxiliary Power Supply FET Switchover Failure Detection

The patent replaces the mechanical/diode-based switchover control with FETs (Field Effect Transistors) that can be controlled by voltage signals. This substitution enables active control of the switchover mechanism, allowing the system to not only switch power sources but also to detect and judge failures through voltage monitoring at specific nodes, thereby resolving the contradiction between structural simplicity and failure judgment capability.

The patent implements feedback by monitoring voltages at specific nodes (such as the drain of the first bypass FET and the connection point between FETs) and using this information to judge the status of circuit components. The controller uses voltage threshold comparisons to detect open-circuit or short-circuit failures, creating a closed-loop system that provides both switchover control and failure detection, thus maintaining reliability while managing complexity.

The FETs in the patent serve multiple functions: they act as switchover control elements for power source selection and simultaneously serve as sensing elements for failure detection. By making the FETs multi-functional, the patent reduces the need for separate detection circuits, thereby limiting the increase in overall device complexity while maintaining improved failure judgment capability.

The circuit uses its own operational parameters (voltage drops across FETs during normal operation) for self-diagnosis. The controller monitors voltages that naturally occur during FET operation and uses these to judge component failures, eliminating the need for additional dedicated detection hardware and thus limiting complexity increases.