Power Supply Circuit Operation Theory; Block Diagram - BenQ MP611 Product Service Manual

4.2 Blower Fan
Blower fan is designed for cooling the lamp tip and lamp burner. The speed of blower fan is controlled and
monitoring by MCU.
4.3 Rear Fan
Rear fan is designed for cooling the whole system except tip and burner of lamp. The speed of rear fan is controlled
and monitoring by MCU.
4.4 Temperature Sensor
There are three temperature sensors built on the system. One is seated at fresh air intake area. One is seated on
DMD heat-sink. And the other one is near by the Lamp Box. The sensor is binary junction diode, and there is chopping
bias current on it. MCU will do polling for each sensor and fan speed, and execute cooling V-T curve control program in
order to feed the environment situation changing requirement.
4.5 Fan Controller
The fan driver device consists of I2C interface, thermal sensor interface, fan current output
interface, and the tachometer interface. MCU access fan driver device by I2C interface. Thermal
sensor interface is analog small sensitive signal. The temperature measurement principle is
calculating the biasing current of diode to figure out the temperature parameter of the diode.
Chapter 5 Power Supply Circuit Operation Theory
5.1 Overview
The power supply unit includes EMI board, PFC board, DC/DC board (built on Fan board), and
Ballast board.
The EMI board has EMI filter circuit to reduce EMC noise coupling to AC line. The PFC board
circuit supply AC line power factor correction function. DC/DC board converts primary voltage to
secondary DC low level voltage for system using. And Ballast board generates the lamp ignition high
voltage to ignite the lamp, maintains the stable power consumption of lamp, and synchronizes the
lamp sequence with DLP color index sequence.
Line
EMI
Input
filter
5.2 General Specification
Input voltage : AC 90~264V
Input Frequency: 47~63Hz

Block Diagram

Bridge
Rectifier
Power
Factor
Correction
380VDC
2.5VDC
Switching
Power
5VDC
Supply
12VDC
140
380VDC
To Ballast