What bias current have you got the drivers operating at?
For a big PA style amplifier one often sees the output devices running at near zero bias current to keep them cool with a too small heatsink.
But that still leaves the drivers running at high quiescent power.
Does this latch and to reset requires power on and off? How much DC is required before it latches?
That protect is flawed.
The 10k collector load for the third transistor, bc546, is far too high. It only allows ~1.1mA to flow to the relay driver. The relay driver should be saturated when used as a switch.
The two transistor DC detect has very poor detection of -ve going pulses.
It does not latch.
It does delay self reset due to time required to recharge the 100uF to trigger voltage.
And the last transistor does not need to be a medium power device, many To92 will do that switching duty.
Assuming an Ib=4mA with Vbe=0.7Vbe and Ic=36mA with Vce=0.06Vce
the total driver dissipation is 0.7V*0.004A + 0.06V*0.036A = 0.00496W = ~5mW
The pre-driver has a similar dissipation ~4mW
Why did you attach such a big pic?
The 10k collector load for the third transistor, bc546, is far too high. It only allows ~1.1mA to flow to the relay driver. The relay driver should be saturated when used as a switch.
The two transistor DC detect has very poor detection of -ve going pulses.
It does not latch.
It does delay self reset due to time required to recharge the 100uF to trigger voltage.
And the last transistor does not need to be a medium power device, many To92 will do that switching duty.
Assuming an Ib=4mA with Vbe=0.7Vbe and Ic=36mA with Vce=0.06Vce
the total driver dissipation is 0.7V*0.004A + 0.06V*0.036A = 0.00496W = ~5mW
The pre-driver has a similar dissipation ~4mW
Why did you attach such a big pic?
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