Technalogix TAV-1000, Руководство пользователя

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VI-1
Section VI – Monitor and Control System
Control Board Overview (Series IIH)
The control printed circuit boards (PCB) are located at the front of each enclosure connected directly to the back
of the liquid crystal displays (LCD) and are identified as Series IIH PCBs. The main purpose of the Series IIH
PCB is to monitor the RF power and the DC supply voltages in the power amplifier and filter enclosures and to
monitor the DC supply voltages in the power supply enclosure. In all cases, a DC voltage proportional to the
parameter being sampled is conditioned, protected, buffered, and then run into an analog-to-digital converter
(ADC) where software processes the signal. The software processing determines if the parameters are within the
predetermined safe operating levels and displays the parameters on the LCD for monitoring purposes. The
Series IIH PCB can be broken apart into (5) main component areas: the power supply, interface, signal
processing, display, and microcontroller. Schematics are found later in this section.
Power Supply Components
There are (4) power supply voltages generated on the Series IIH PCB:
1. +5Vdc for all logic and general purpose PCB supply voltage.
2. +4Vdc for the LED backlighting on the LCD
3. -4Vdc for the contrast voltage required by the LCD
4. +8Vdc for the directional coupler supply
The +5Vdc is generated from a small switching power supply comprised of C1, C2, D2, L1, and U1. This power
supply accepts DC input voltages up to 40Vdc and o5Vdc at 1Adc. This voltage is always on, as the
ON/OFF pin on U1 is hard-wired to the ‘on’ configuration.
The +4Vdc is generated from a small switching power supply comprised of components C3, C4, D3, L2, and U2.
This power supply accepts DC input voltages up to 40Vdc and o5Vdc at 1Adc. The voltage is then
dropped to +4Vdc through R1. This backlight voltage can be turned on and off via the ON/OFF pin on U2. The
PCB is setup in a manner that allows this voltage to be hard-wired ‘on’ all the time or controlled from the
microcontroller through latch U11. This selection is made with jumper J2.
The -4Vdc is generated using a switched capacitor voltage converter design, using components C6, C7, R2, R3,
U4, and VR1. U4 a5Vdc from the general p5Vdc supply and generates -4Vdc. This voltage is
then dropped across the voltage divider (R2, R3) to generate the contrast voltage specific to the LCD in the
system.
The +8Vdc required by the directional coupler is generated with a standard linear voltage regulator, U3. C5
cleans up any ripple or noise that might be on the output voltage.