Customer returns can be a major headache for power supply and power system manufacturers. Returns are often provided with limited and ambiguous information regarding the failure mechanism and with vague details about the environmental conditions and the ‘scene of the crime’. The time-pressure to diagnose and report comprehensive failure analysis based on sketchy information continues to contract. The cost associated with debugging and fixing issues naturally increase as the design progresses to different stages from the prototyping to production and to the end customer – not considering relationship damage and credibility.
In addition, a significant percentage of customer returns appear to be ‘no-fault-found’ returns. Such returns can often be dismissed and never correctly diagnosed but risk masking real failure mechanisms in the end customer system. For example, any failure causing an over-temperature trip will shut-down in the customer equipment but when returned to the manufacturer may appear to function normally.
The problem can be solved using built-in ‘Black Box’, similar in concept to an airplane flight recorder and capable of capturing critical information prior to shut-down. This article describes how the ADP1055 advanced PMBus digital controller for isolated power supply systems uses its internal Black Box to record and store critical information. The data can be used by power system manufacturers and end-system users to improve diagnosis of field customer returns and improve the robustness of the qualification process.
Black box operation
The Black Box feature of the ADP1055 can record to the EEPROM vital data about the faults that cause the system to shut down. The Black Box diagnostics tool can be considered in two parts: Firstly the ‘First Flag ID’ feature records the first instance of failure such as over current/voltage/temperature etc.; and secondly, as the controller encounters such a fault a snapshot of the telemetry is captured (see Figure 3). This information is saved to the embedded non-volatile EEPROM, where it can be later retrieved for