Sony RM-PJM610, Руководство по обслуживанию, Страница: 71 / 177

3-18
VPL-PX20/PX30
Fig. 4 show a simple block diagram of the active filter control IC2100. The current flowing to MOS-
FET Q2100 is detected by the sense resistor R2106. When this current reaches the threshold value
corresponding to the peak current flowing to the choke coil L2100, the comparator turns OFF the
MOS-FET Q2100. The threshold value is sent to the comparator as the product of the AC voltage
waveform and control amplifier output voltage V0. The MOS-FET Q2100 maintains the OFF state
until the choke coil L2100 and diode S2108 current becomes zero. The output is maintained at
358
±
10V by the PWM control of the switching. This output setting is performed by the R2127 to
R2133 voltage-dividing resistor.
4. Timer function
As a watchdog timer function is equipped inside the IC2100, no external oscillator is required. When
the current flowing to the choke coil L2100 reaches zero and the drive output becomes OFF for more
than 620 us, the timer automatically starts or restarts the pre-converter.
5. Internal over-voltage comparator
To prevent abnormal output voltages, the control ICIC2100 is equipped with an over-voltage
comparator. This comparator turns ON at initial startup, when the load changes suddenly, and when
the output ripple increases. The over-voltage comparator monitors the peak output voltage of the
converter, and turns OFF the MOS-FET Q2100 immediately when the reference value is exceeded.
The threshold value of the comparator is set to 1.08V in the control IC IC2100.
Multiplier Input
GND
Vref
1.8V
1.5V
Multiplier
Delay
Timer R
16V
13V
UVLO
2.5V
Reference Voltage
Source
RS Latch
Current Sence Comparator
Over Voltage Comparator
Differential
Amplifier
Voltage Feedback
Input
Compensation
Current Sence
Input
Drive Output
Zero Current
Detector IN/OUT
V
CC
Quick Stert
6.7V
1.2V
1.6V
Zero Current
Detector
Fig. 4 Simple Block Diagram of IC2100