Toshiba 4580, Service Manual

Page: 130 / 379

Mar. 1999 © TOSHIBA TEC 9 - 3 6570/5570 PAPER FEED SYSTEM
■
Pulse motor drive circuit (Constant voltage bipolar type)
Aligning motor (M17) (RGT-MOT) is driven by 2SD1415A of Q2 to Q5 on the logic PC board. The circuit
is shown below.
Construction of motor drive
In the case of 2-phase excitation, AB, BA, AB, and BA will be successively excited. While transistors QA
and QB are ON, current from the +24V stabilized power supply will flow into phases A and B.
Next, while QA is OFF and QA is ON, the current which flowed through phase A will be cut off owing to the
disappearance of a flow path. At this point, however, phases A and A will be inductively coupled, causing
the current from the 24VDC power supply to be diverted through diode DA to phase A, in the direction
marked X. When the currnet flowing in this direction becomes zero, current will flow through QA to excite
phase A.
At the instant when QA goes OFF, the current which flowed through phase A abruptly decreases, causing
a high voltage to appear at the collector of QA. Because of Zener diode ZDA, however, the collector
voltage is held at the Zener voltage, protecting transistor QA and diode DA.
ZDB ZDB ZDA ZDA
DC
24V
B B
QB QB QA QA
DB
2SD1415 X 4/STA404A
DB DA DA
A A
X