Overvoltage protection circuit

The protection circuits of power amplifiers
mainly include overvoltage protection and overload protection. In addition, overheating protection circuits are provided in the internal circuits of some integrated power amplifier circuits .
    The figure shows an overvoltage protection circuit . In the circuit, VT1 and VT2 are the two output tubes of the main power amplifier , and VD3 and VD4
are protection tubes and zener diodes.
    The working principle of this circuit is that the breakdown voltage of VD3 and VD4 is slightly greater than the winning current operating voltage + Ucc. In this way, during normal operation,
VD3 and VD4 do not break down, which is equivalent to an open circuit. If high voltage occurs accidentally, VD3 and VD4 will break down and clamp the voltage to achieve
the purpose of protecting the power amplifier output tube.