In-car audio amplifier (3):

As described in Part 1, the temperature sensor is linked to the protection circiut in the inverter via K1 (pins 2, 4, 6 and 8). lts output is compared with a reference value, set by P2, in lC3b. Any noise on the connections is filtered out by R32-C16 to prevent spurious actuation of the circuit. Hysteresis is provided by R31, which means that the heat sink must cool down by about half a degree before the amplifier is switched on again, In practice, the temperature protection circuit should be set to switch off the supply when the temperature of the heat sink reaches 65-70 °C.