High power opamp-based constant current source circuit
The input to R22, labelled OC1A appears to set the output current level. At a guess, it's a 0-5 volt signal. The two 100k resistors drop this to 0 to 2.5 volts. This is important because

PA7 appears to be a digital signal which forces the current to zero by forcing the - input of DA1:2 above the 2.5 volt maximum of the + input, driving the output of DA1:2 low, thereby turning off the FET. In normal operation, PA7 is held low, and the diode is back-biased, so it has no effect. R37 is there as a safety feature. If PA7 is completely absent, such as might happen if the source of PA7 loses power or there is a cable break, R37 pulls up the anode of VD2 and forces the output current to zero.