Audio Power Amplifier Output Stage Protection

摘要

This paper reviews a progression of circuits used for protecting bipolar power transistors in the output stages ofaudio power amplifiers. Design oriented methods of determining the protection locus are shown in a mathematicaland graphical procedure. The circuits are then expanded from their standard configurations to allow for transientexcursion beyond steady state limits, and thermally dependent protection limits, to better match the protectionlimits to the actual output stage capability. This allows the protection scheme to prevent output stage failure in theleast restrictive way.A new method is shown for achieving a junction temperature estimation system without the use of a multiplier.