Toshiba 4560, Service Manual

Page: 71 / 369

Nov. 1997 © TOSHIBA 7 - 9 4560/4570 OPTICAL
In the case of the excitation of A phase, øA becomes “L” level and F2 comes ON, the same operation is
performed.
The limit of winding value is changed in high torque and low torque by the D/A output. In low torque the
current is lower, in high torque the current is higher.
Low torque : I
OH
= 1.2 (A)
High torque: I
OH
= 1.35 (A)
– Process when the A phase is excited –
1 øA phase becomes “L” level (øA is “H” level).
2 Reverse input E of the comparator (IC1) is applied with the reference voltage which depends on
the resistance-divided voltage of the R12, R14, and the R18.
Non-reverse input B is “L” level. Therefore, the output C of IC1 becomes “L” level.
3 According to step 1 and 2 , D of IC2 becomes “H” level, and F1 is turned ON (conductive
condition).
4 Current flows into the coil A from the power supply of +24V, and it gradually increases.
5 The terminal voltage of the current detection resistor R11 increases, and C becomes “H” level and
F1 goes OFF from the moment when voltage B becomes higher than voltage E .
6 Because the winding method of coil A and A is bipolar winding, the energy stored in coil A is induced
in coil A, and is discharged using the coil A.
That is, A current flows in the direction of DG (Drive Ground), R7, F2 diode and coil A.
7 When the voltage stored in the condenser C1 lowers, and becomes lower than voltage E , C
becomes “L” level and F1 comes ON again, and the winding current of A phase increases.
8 In this manner, the ON/OFF operation of the motor current (constant current chopping operation) is
repeated.
Motor input current waveform
I
OH
=1.35(A)
0 (A)
1.35