Holtek AN0315E, Using Manual

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Using the HT45FH3T in the Active 3D Glasses
7
Boost Circuit
Use the BOOST_ON (MCU Pin 8, OUTH) PWM signal to control the Q1 on/off state. The
energy stored in L1 is transferred and stored in C1 and C2, which together can generate
a 10V boost voltage. A divided voltage generated using R6 and R7 is fed back to the
MCU OVP function to maintain the boost out voltage at the correct level.
LCD Lens Control
The 3D glasses LCD lenses have 3-Line and 4-Line types. In this application, 3-Line
controlled lenses are used. For the level shift circuits, whose power is supplied by the
boost circuit, increase the LCD control voltage to 10V for the lens on/off control.
Battery Voltage Detect Circuit
Use the ADC to check the MCU internal band gap voltage, and select the ADC reference
voltage to come from VDD. If the battery voltage falls below 3V, the VDD voltage will also
fall below 3V. The band gap value detected at this moment will be higher than before, this
indicating a VDD low voltage condition.
LED used as a Low Voltage Indicator
Main control MCU
The main control MCU is the HT45FH3T-1, which has both integrated PWM and OVP
circuits.
IR Receiver Circuit
In this circuit, tiny signals received by the IR photodiode will be filtered, amplified and
integrated to generate the digital signals that can be processed by the MCU.