IC-SP-06027 R1
5-5. Operation of the output IGBTs of the VSP-input type
(Applicable models: ECN30102, ECN30105, ECN30107, ECN30204, ECN30206, ECN30207)
(1) PWM operation
•
PWM signals are generated by comparing the VSP input voltage and triangular signal (CR pin voltage).
•
Chopping with PWM is conducted by the lower arm. (See Fig.5-10.)
VSP input voltage > triangular signal; the lower arm IGBT on
VSP input voltage < triangular signal; lower arm IGBT off
•
The PWM duty varies linearly between the bottom limit (VSAWL = typ. 2.1V) and the top limit (VSAWH =
typ. 5.4V) of the triangular wave amplitude level. It becomes 0% at VSAWL, and 100% at VSAWH.
VSAWH
(typ. 5.4V)
Triangular wave signal
(CR pin voltage)
VSP input voltage
VSAWL
(typ. 2.1V)
Lower arm IGBT
OFF
ON
OFF
ON
OFF
ON
OFF
ON
Motor coil current
Power supply current IS
Fig. 5-10. Timing chart of PWM operation
(2) Output all-off function
(a) Function description
•
When the input voltage of the VSP pin reaches or goes below the all-off operation voltage (Voff = typ
1.23V), this function turns off all the output IGBTs. The operation of the output IGBTs with regard to the
VSP input voltage conforms to Table 5-5.
Table 5-5. Operation of the output IGBTs with regard to VSP input voltage
VSP input voltage
0V≦VSP＜Voff ( typ. 1.23V)
Voff (typ. 1.23V)
≦VSP＜VSAWL
(typ. 2.1V)
VSAWL (typ. 2.1V)
≦VSP
All off
As per hall signal input
As per hall signal input
Top arm IGBT
All off
All off
As per hall signal input
Bottom arm IGBT
(b) Precautions
•
When the output all-off function is activated while the motor is rotating, a regenerative current is
generated in the VS power supply, in some cases resulting in the VS power voltage rise. Keep the VS
pin voltage equal to or below the maximum rating. Attention is particularly needed, when the capacity
between the VS and GND is small, where the voltage is more likely to rise.
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