Epson SQ-B50/2550 Technical Manual page 114

REV.-A
<
PLL Control>
The method by which PLL control is carried out by the control circuit may be explained as follows.
Movements away from the set speed are detected based on a phase comparison of the positive-going
edge of the A phase signal (leading signal) against the set speed signal (the requested frequency).
Energizing signals which correspond to these errors are determined and are sent to the motor. These
signals control the ON or OFF state of motor energizing, and thereby maintain the set motor speed.
L-
Setting Speed
,J
1"'--------:c--------''1
Internal
Speed
Signal
Encoder A
Phase
Motor OFF
Drive ON
Signal
Figure 2-48. PLL control (at normal speed)
Encoder A
Phase
Internal
Speed
Signal
Motor
Drive
Signal
Internal
Speed
Signal
OFF
ON
f
Figure 2-49. PLL control (at accelerated speed)
L. Setting Speed
..J
I"":---------=------.:.---'l
L.---_f f
___f
Encoder A
Phase
Motor Drive
Signal
OFF
U
ON
~_f
u
~--+
u
___t
u
Figure 2-50. PLL control (at reduced speed)
2-46