Sub Voltages And Over-Voltage Protection - Panasonic TC-32LX70/70 Technical Manual

SUB Voltages and Over - voltage Protection
SUB Voltages and Over - voltage Protection
The AP Board is responsible for the regulation, distribution and dissemination of all secondary
voltages derived from the 24V output of the P Board. During standby operation, the 24V output of the P board
biases the transistor Q7208 into operation, causing its collector to become "low". The low at the collector of Q7208
causes the transistors Q7226, Q7227, and Q7450 to turn off. As a result, IC7205, IC7209, and IC7233 go into
operation to immediately provide the Sub_5V, DT9V, BT30V, and HQ 3.3V output.
The over-voltage protection circuitry affiliated with each of the regulators monitors for excessive current and over-
voltage conditions. It is designed to turn off the AC power by disabling the SUB_ON signal needed to turn on the AC
relay.
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