Battery Protection Switch Fault Diagnosis Without Current Sensing

The patent extracts the problematic parasitic diode function from the conventional power transistor structure by using separate control transistors (first control transistor and second control transistor) that do not have parasitic diodes affecting voltage measurement. This allows the main power switches to be controlled without the measurement accuracy degradation caused by parasitic diodes in the original transistor structure.

The patent introduces intermediary control transistors that act as mediators between the control signal and the power switches. These control transistors enable precise voltage measurement and switch control without the parasitic diode effects that would otherwise interfere with measurement accuracy, thus resolving the contradiction between simple structure and measurement precision.

The patent performs preliminary voltage measurement during normal operation to establish baseline values before any fault occurs. By pre-storing these voltage values and comparing them during diagnostic mode, the system can detect switch damage regardless of whether the battery is currently charging or discharging, thus enabling diagnosis in all operational states.

Instead of measuring current to diagnose switch damage (which requires active charging/discharging), the patent inverts the approach by measuring voltage at specific nodes and comparing it against stored reference values. This voltage-based diagnostic method works in reverse logic to current measurement, enabling diagnosis during idle states when no current flow occurs.

The patent makes the voltage measuring circuit multi-functional by using it for both normal battery voltage monitoring and switch damage diagnosis. The same measuring circuit measures voltage at first and second nodes during operation, and these stored values are later used for diagnostic comparison, eliminating the need for separate diagnostic hardware and reducing overall device complexity.

The system performs self-diagnosis by using its own existing voltage measurement capabilities and stored reference values. The battery management device compares currently measured voltages against pre-stored baseline values to automatically detect switch damage without requiring external diagnostic equipment, thus achieving high measurement precision without proportionally increasing device complexity.