IC-SP-06027 R0
5. Functions and operational precautions
5-1. Protection function
(1) Detection of VCC under voltage (LVSD operation)
·
When the VCC voltage goes below the LVSD operating voltage (LVSDON), the output IGBTs of the top
and bottom arms are all turned off regardless of the input signal.
·
This function has hysteresis (Vrh). When the VCC voltage goes up again, the system goes back to a
state where the ouput IGBT operates according to the input signal at a level equal to or exceeding the
LVSD recovery voltage (LVSDOFF).
VCC voltage
LVSD recovery voltage
(LVSDOFF)
LVSD operation voltage
(LVSDON)
LVSD operation
LVSD recovery
LVSD hysteresis
(Vrh)
Operation according
to the input signal
IGBT
operation
All off regardless of the
input signal
(LVSD operation status)
Operation according to
the input signal
Fig. 5-1. Timing chart for detection of VCC under voltage (LVSD operation)
(2) Current limitation
(a) Operation description
·
The system monitors the current flowing through the shunt resistance Rs at the RS pin (see Fig. 5-2).
When the reference voltage for current limitation (Vref = typ. 0.5V) is exceeded, the IGBT of the
bottom arm is turned off.
·
Reset after current limitation is performed in each cycle of the internal clock signal (VTR pin voltage).
(See Fig.5-3.)
VS
VS1 VS2
-
+
Vref
RS
GH1
RS
MU
MV
MW
Motor
GH2
Is
Fig. 5-2. Current of shunt resistance (typical)
-
13
-