Zenith L30W26 Service Manual page 26

BLOCK DIAGRAM
3-1. Signal flow
If the AC Input voltage(1) is confirmed, this Input voltage is adjusted as a DC wave by the EMI FILTER(2) and the first
adjusting part(3). This adjusted wave is input to PFC(4, Power Factor Correction) and the output voltage(+390Vdc) by the
PFC circuit becomes a Main Input voltage of MAIN(5), STANBY(10) Switching part.
Input voltage is input to Switching part(5, 10) which outputs a High Voltage spherical wave with high frequency from
Switching by elements such as FET, PWM IC.
To keep the secondary adjusted voltage regular and safe with changing Input voltage and Output load, the output voltage is
watched and feed back to switching part(5, 10) through the control circuit(9).
BLOCK 2 works as a forward converter by receiving Input from BLOCK 1. It supplies MAIN DC(+24V, +12V) voltage and the
Step Down circuit(8) supplies +18V.
BLOCK 3 works as Flyback converter by receiving Input from BLOCK 1 and supplying +5V for Stanby.
The protection circuit is built into the switching part(5, 10) to protect over electric-current, short, and over voltage of the
secondary output. This circuit protects the output and sticks the Terminal Switch(15) to a radiator while the PFC and protect
against fire or other accident by turning the AC voltage off while overheating.
To minimize power consumption, if the OFF signal is transmitted to PFC part(4), Main part(5) through the control circuit
connected from the Main board to the Power board, only the +5V circuit for Standby works and others are OFF.
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