Heater Control Circuit - Toshiba e-STUDIO2006 Service Manual

3.14.5

Heater Control Circuit

[ 1 ] Configuration
In this equipment, the surface temperature of the fuser roller is controlled by turning ON/OFF the 2
heater lamps (center and side) which have different heat-generating positions with the command from
the engine-CPU on the main board.
The surface temperature of the fuser roller is detected by 3 thermistors (center, side and edge) and
then the information of the temperature is transmitted to the engine-CPU and each control circuit.
Based on the detected temperature, the engine-CPU transmits the control signal of the heater lamp to
the control circuit (TRC: Triac) of each heater lamp on the switching regulator via the temperature
control circuit. The power supply to the fuser roller is thus controlled by driving TRC. The temperature
control circuit detects the overheating of the fuser roller. In case that the surface temperature of the
fuser roller has exceeded the specified temperature, the temperature control circuit turns the heater
lamp OFF. If the temperature control circuit does not function for some reason and the fuser roller is
abnormally overheated as the result, a relay OFF circuit transmits a relay OFF signal to turn off the
relay, and to turn the power OFF forcibly.
If the temperature control circuit does not function for some reason and the fuser roller is abnormally
overheated as the result, a forcible power-OFF circuit transmits a reset signal to the power switch to
turn the power OFF forcibly. In addition, if these control circuits do not function with thermistor
abnormality or other reasons and the fuser roller is abnormally overheated as the result, 2 thermostats
(front and center ones in the fuser unit) shut off the power supply to the heater lamps to protect the
equipment.
<20L/23L/25L, 20H/23H/25H>
Fuser unit
Fuser front Fuser center
thermostat thermostat
(THMO2) (THMO1)
Front
Fuser roller
Center heater lamp (LAMP1)
Side heater lamp (LAMP2)
Center Side
thermistor thermistor
(THMS1) (THMS2)
A/D
converter
CPU
Relay OFF circuit
© 2013-2017 TOSHIBA TEC CORPORATION All rights reserved
Switching regulator (LVPS)
Rear
Center heater lamp
control circuit (TRC1)
Side heater lamp
control circuit (TRC2)
Edge
thermistor
(THMS3)
ASIC
Temperature control circuit
Relay OFF signal
Fig. 3-53
e-STUDIO2006/2306/2506/2007/2307/2507/2303A/2303AM/2803AM/2309A/2809A
3 - 65
Noise
filter
Relay
MAIN board (MAIN)
L
N
Main switch
(SW1)
AC line
DC line
OUTLINE OF THE MACHINE
3