AN1905 ST Microelectronics, Inc., AN1905 Datasheet - Page 23

• Manufacturer Part Number: AN1905
• Description: St7mc Three-phase BLDC Motor Control Software Library
• Manufacturer: ST Microelectronics, Inc.

Figure 11. Configuration at max. current
Therefore, the maximum current can be calculated:
Previous formula applied to the starter kit leads to:
The current sense resistor value has to be adjusted when a different working range is needed.
It is then necessary to decrease it when the current requirement is higher, or to increase it
when the current requirement is lower. It is also possible to adjust the OPAMP gain, but it has
to be remembered that:
– A High-gain OPAMP configuration may decrease EMC performance.
– A low-gain OPAMP combined with a high current sense resistor value will induce higher pow-
– The power stage of the starter kit has been designed to handle power up to 1KW. For higher
3.6.2 Interpreting the current feedback/settings in the GUI
Settings related to current values on the GUI are treated as if the current sensor value were a
47 milli-Ohm type (with OPAMP gain equal to 11). When using a different resistor value, set-
tings concerning current can’t be read/written directly but have to be calculated manually
using a proportional coefficient equal to:
The actual current information is the one shown on the GUI multiplied by the proportional co-
efficient ‘K’ (See
er loss (into the resistor).
power, a bigger heat sink and current capability IGBTs or MOSFETs may be required.
ST7MC THREE-PHASE BLDC MOTOR CONTROL SOFTWARE LIBRARY
Figure 12
5 Volts
&
Figure
I
I
max
max
K = 47 milli-Ohm / new value
= V
= 5 / (11 x 0.047) = 9.67 amperes
13).
saturation
Uout
OAZ/MCCFI1
MCCREF
comparator
clock
PWM freq.
/ (OPAMP
OPAMP
X11
+
-
Usense
gain
Set
R
x R
T4
47 milli-Ohm
sense
)
A
T1
HV
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