Bosch VCU, Manual

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Power Stages | 12
Bosch Motorsport Vehicle_Control_Unit_VCU_Manual 69 / 136
12 Power Stages
Power stage details
The Vehicle Control Unit VCU uses integrated power stages with built-in diagnosis. For the
high side switches, overload-behaviour (mode “bulb” or “DC motor”, restarts etc.) is de-
termined inside the IC itself.
A measurement shunt is used for current measurement. The low side switches come with
a switchable, discrete free wheeling diode. Current measurement is done inside the IC;
one common value for two switching channels is available.
Diagnostics
Low side:
– shortcut to GND in switched off state
– overcurrent
– shortcut to U_batt
– open load
– overtemperature (power stage)
High side:
– shortcut to GND
– overcurrent/ overtemperature
– shortcut to U_batt in switched off state
– open load
– current measurement and plausibilisation in CCA
Suggestion for the implementation of a current control
There is no analogue circuitry for a current control. However, the current measurement
values can be used for the calculation of an appropriate pwm dutycycle in the Customer
Code Area (CCA).
Current measurement is executed at a 1 kHz frequency, the reconfiguration of the pwm
dutycycle in the blue SIMULINK blocks can be done in different frequencies including a
1 ms raster.
For a current control using the low side switches, an additional external current sensor
needs to be read. The current measurement is not sufficiently accurate and is only avail-
able for 4 of the 8 channels. (The free wheeling diode needs to be activated.)