Mermaid:Mechanic L1 Pro Failure Sequence

%%{init: {'theme':'default', 'sequence': {'width': 50, 'height': 30, 'actorMargin': 20, 'boxMargin': 5, 'messageFontSize': 10, 'noteFontSize': 10}}}%% sequenceDiagram participant User participant PowerButton participant QX9920 participant Q1 participant LED User->>PowerButton: Turns lamp ON directly Note over PowerButton,QX9920: Timer bypassed -<br/>no auto cutoff<br/>scheduled PowerButton->>QX9920: VIN applied, EN held<br/>high continuously QX9920->>Q1: DRV switches gate<br/>at full duty Q1->>LED: Sustained drive<br/>current, no rest loop Extended runtime,<br/>no shutoff Q1->>Q1: Conduction + switching<br/>losses generate heat Note over Q1: Heat dissipation<br/>can't keep pace end Note over Q1: Junction temp exceeds<br/>rated max Q1-->>Q1: Thermal failure -<br/>commonly fails shorted D-S Q1->>LED: Uncontrolled current -<br/>CS feedback no longer limits Note over LED: LED experiences<br/>overcurrent stress

%%{init: {'theme':'default', 'sequence': {'width': 50, 'height': 30, 'actorMargin': 20, 'boxMargin': 5, 'messageFontSize': 10, 'noteFontSize': 10}}}%%
sequenceDiagram
    participant User
    participant PowerButton
    participant QX9920
    participant Q1
    participant LED

    User->>PowerButton: Turns lamp ON directly
    Note over PowerButton,QX9920: Timer bypassed -<br/>no auto cutoff<br/>scheduled
    PowerButton->>QX9920: VIN applied, EN held<br/>high continuously
    QX9920->>Q1: DRV switches gate<br/>at full duty
    Q1->>LED: Sustained drive<br/>current, no rest

    loop Extended runtime,<br/>no shutoff
        Q1->>Q1: Conduction + switching<br/>losses generate heat
        Note over Q1: Heat dissipation<br/>can't keep pace
    end

    Note over Q1: Junction temp exceeds<br/>rated max
    Q1-->>Q1: Thermal failure -<br/>commonly fails shorted D-S
    Q1->>LED: Uncontrolled current -<br/>CS feedback no longer limits
    Note over LED: LED experiences<br/>overcurrent stress