Toshiba 4560 Service Manual page 313

(Description of STK6713BMK4 Internal Circuit Operation)
Vcc1
L1
1 1
ON OFF
+5V
L2
Vcc2 A A
1 2 3
i Q1 j i Q2 j
F1 F2
IC2
IC2
The figure above shows the equalizing circuit of the STK6713BMK4. The circuit comprises a phase
driver, comparator, PWM excitation selector and current detection resistor.
When a L-level signal is input to φ A and a H-level signal is input to φ A
IC1 (comparator) becomes L-level, the output S of IC1 becomes L-level. As current iON of the A coil
passing through Q1 increases, the voltage across the terminals of source resistor R7 also increases,
output becomes H-level from the moment that the voltage across pin 8 and R
S
Q1 is turned OFF.
The energy accumulated at coil L1 of the pulse motor is induced to L2. At this time, the current flowing to
L2 is taken as i . The energizing time of i
OFF
tors C1 at both ends of R3 becomes equal to the voltage across both terminals of R
is equal, output is inverted, and becomes L-level, so motor coil current i
S
level of R02 again. In this way, the motor current is turned ON/OFF, that is, current chopping operation is
repeatedly carried out.
The same operation is carried out for other phases.
(Motor rotation amount input circuit)
This circuit is for improving stop positional accuracy by counting the number of steps of the pulse motor.
A pulse of cycle twice the step of the pulse motor is output from the output obtained by inputting PMA1
and PMB1 from amount the 2-phase excitation pulses to EXOR (IC13). When both edges of this pulse
are detected by the CPU interrupt terminal, the number of motor steps can be counted.
Nov. 1997 © TOSHIBA
R01
A A Td1
15 13 8
C1
IC2
R3
R1
IC2
-
+
IC1
R5
D1
S
is the time up to when the voltage accumulated at capaci-
OFF
R02
Vref NC Vref Td2 B
9 12 11 10 14
C2
R4
R2
-
+
IC1
R6
D2
R7 R8
–
, Q1 turns ON. As the + terminal of
18 - 55
B B B
16 7 6
F4 F3
IC3
IC3
IC3
IC3
becomes equal, and
02
. When the voltage
02
increases to the voltage
ON
4560/4570 RADF
PQ SQ
4 5