RL78/G1F Motor Driver Board GB01
User's Manual
R12UT0012EJ0100 Rev.1.00
Page 14 of 32
20.10.2020
8.2 Current Detection Circuit
The current detection circuit is integrated to measure the U-phase, V-phase, and W-phase current. The
current detection circuit is configured by mounting a shunt resistor for the U-phase, V-phase, and W-phase.
The voltage drop generated when the current passes through the shunt resistor is amplified by the
operational amplifier and then input to the microcontroller. The equation (1) below shows the relationship
between the current Iin running through the shunt resistor and the voltage Vout input to the microcontroller.
Vout[V] = Iin[A] × Rs[
Ω
] × 5 + 2.5
(1)
-
+
Iin
Vout
I
U
_OPA
2.0k
Ω
2.0k
Ω
20k
Ω
20k
Ω
10k
Ω
Rs
5V
Rs : Shunt resistance
Iin : Current flowing through the shunt resistor
Vout : Voltage applied to CPU card connection terminal
I
V
_OPA
I
W
_OPA
Figure 8-2 Schematic Diagram of Current Detection Circuit
Also, a DC link shunt resistor is mounted for 1-shunt current detection, which enables detection of the
overcurrent by using the RL78/G1F internal PGA and current detection comparator.
Inverter
circuit
DC POWER
INPUT
-
+
A/D Converter
CMP0
PGA
PGAIN
PGAGND
Figure 8-3 Connection of PGA and Inverter Control Circuit
-
+
D/A
Converter
Idc
Figure 8-4 Overcurrent Detection Using Internal PGA and CMP0
