For injector management, the following power sources are used:
a. 12V supply (onboard) source: low-voltage;
b. 60 .. 65V supply source: high-voltage.
In the picture – the management signal of the B58 injector (idle, warmed-up engine).
Blue color: connection of the high-side switch;
Yellow color: connection of the low-side switch.
High-side switches are common for each of the two injectors. Individual for each injector: low-side switch.
To manage the injector:
a. first, one of the two injectors is chosen by opening its low-side switch;
b. to open the injector, a 60 .. 65V voltage is supplied to it by opening the high-voltage source high-side switch. The length of the impulse is around 300 us;
c. for a short moment (around 20 us), the high-voltage source high-side switch is closed;
d. the low-voltage source high-side switch is opened (12V voltage is supplied to the injector), which determines how long the injector will be open (in this image – around 250us);
e. the low-voltage source high-side switch is closed;
f. the low-side switch is closed. The injector closes.
Here is the image of how the voltage on the injector outputs looks like (relatively; red color):
Several notes:
a. increased voltage (60 .. 65V) is chosen to open the injector quickly (speed of the current increase in the injector is directly proportional to the supplied voltage);
b. at the moment, when the injector should be closed, all switches are closed (low-side too). Low-side switch has a bootstrap diode, which is connected (with a Cathode) to a high-voltage supply source. Such a connection ensures the energy recirculation back in the high-side supply source (requirements for the power of this source reduced) and guarantees maximally fast closing of the injector (closing speed/energy dropping is directly proportional to the voltage on the injector outputs).
In the image, we see that the current in the injector reduces (all accumulated energy is returned to the high-side supply source) during 100us.
