Lcd Backlight Inverter/On Board Voltage Regulators; Lcd Backlight Inverter/On-Board Voltage Regulators - Micros Systems Eclipse Setup Manual

Eclipse LCD/Touchscreen Head Configuration

LCD Backlight Inverter/On-Board Voltage Regulators

LCD Backlight Inverter/On-Board Voltage Regulators
Figure 4-11 shows the components used by each circuit in the following descriptions.
The -002 board is shown, but this circuit is used on all versions of the board.
Figure 4-11: Backlight Inverter and On-Board Regulator Components
LCD Backlight DC-to-AC Inverter (-001, -002, and -003)
This description applies to all versions of the LCD/Touchscreen Interface Board. See
Figure 4-11 for a component layout. The backlight inverter circuit is based on U10, an
LT1184 fixed frequency, current mode switching regulator. It is combined with T1,
Q2A, Q2B, D2, D3, and L6 to form a Royer high-voltage converter in a floating lamp
configuration. A floating lamp configuration (there is no galvanic connection to
ground) provides a symmetrical, differential drive waveform to maximize current to
light conversion in the lamp.
The Royer converter is self-oscillating. The transistors conduct out of phase,
switching each time the transformer saturates. Transformer saturation causes a current
spike which is induced into the base drive windings, causing the transistors to change
state.
Lamp current is programed between the REF and ICCFL pins of the LT1184 through a
resistor divider. Drive current is managed by controlling the Royer converter's
primary side converter current through L6 and generating a feedback signal to close
the control loop.
4-14 PCWS Eclipse Setup Guide