Amplifiers DIY line depth discussion elm327

(Biglee_163) : there is a line, is to test the ultimate power tube radiation resistance voltage size, drive the flow detection triode conduction, and finally make protective relay off load, elm327  to protect power tube and speaker. And protection circuit generally with silicon controlled rectifier type state self-hold until after powrefailure eliminate load short circuit relay to closed. More common in discrete power amplifier, such as common protection integrated UPC1237, TA7317.

Another is also testing radiation resistance voltage size, through the drive a triode conduction to make final power tube of input to output neutral short circuit method to protect power tube. This way due to the continuous open load, can make the output intermittence, general IC integrated internal protection with this method. Early discrete power amplifier has the connection.

(locky_z) :

1, the most simple current limiting circuit:
The TR2 TR1 shunt the base  elm327 current, but Tr7 must add current limiting circuit, or protection, Tr7 will die. The power consumption of the circuit line is A rectangle, such as 40 v, protect the current 5.5 A, so, the protection power 220 w, greatly beyond power tube SOA range.

2, single slash VI limiting
Due to the above to power tube SOA requirement is high, therefore, puts forward single curve VI power limitation, join R3. So, Vce increases, the protection current brake value reduced; Vce hours, protection current brake value increase.

Different R3 get different Wholesale obd2 tools slope load line. For example, the following chart of slope 1 line is R3 = 15 k, 2 line is R3 = 10 k, 2 line short circuit, can short circuit current to 2 a.