2-3-10
(2) Heater lamp control circuit
Activation of the heater lamp is dominated by the HEAT signal which is derived by the engine CPU (U1) at its pin #74. When
its level is high, transistor Q8 turns on, photo-triac PC2 and triac TRC1 turn on simultaneously, and the heater lamp is
applied with the primary AC voltage in turn.
Switching of triac TRC1, as affected by the HEAT signal is made in synchronization with the zero-cross signal ZCROSS
which is generated by the power supply unit. The zero-cross signal detector watches the transition of alternating plus and
negative current and detects the zero crosses. This detector derives the resultant ZCROSS signal at its pin #20 of the
engine CPU (U1). Since abrupt change in the current flow can be significantly avoided by synchronizing triac TRC1 with the
zero-cross signal, the possibility of noise due to the primary AC supply is greatly reduced.
Figure 2-3-6 Heater lamp control circuit
HEAT
ZCROSS
Q8
GND
GND
2
3
1
GND
+5V
GND
R52
R57
+
−
393
U6-1
THERMA
98
P72/ANI2
PDL3/AD3
P05/INTP2
74
20
CPU
U1
Power supply unit
Bias
PWB
Engine PWB
High
voltage
PWB
Heat roller
Thermal cutout
Heater lamp
Thermistor
AC input
Triac
(TRC1)
Zero
cross
signal
detection
circuit
+24 V
Heater lamp control circuit
(PC2)
Photo-triac
Service Manual Y104230-6
Содержание d-Copia 18MF Operation
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