Understanding the function of voltage "AC DET"

Understanding the power supply LCD - Series 6

Understanding the function of voltage "AC DET"

Ac voltage suddenly drops dead or eeprom sometimes can cause data errors. Det AC circuits function or turn off the air conditioning is working off Det Mikrokontrol if suddenly the AC input voltage drops (... .ini new personal theory, you know ... because so far we have not received any article that talks about it ......).
Not all power suply LCD has a pin-conditioning Det, and in CRT TV technology can be found on the new models Tv sharp. the circuit AC Det LCD is divided into two parts, the first of section hot chassis.

• This circuit detects the input ac voltage (see picture below) via serial R7111 / 7112/7113
• In normal conditions the voltage at R7109 is greater than 6.8V, so the D7103 zener breaks, there is a base voltage Q7101, Q7101 "on", and the current flows through the diode photocoupler PC7
• If suddenly Ac input voltage drops, the voltage on the R7109 also drops less than 6.8V, Zener not translucent, Q7101 "off", and the current does not exist in photocoupler diode.

 
Both were there on the cold parts of the chassis.

• AC det information through photocoupler is connected to the chassis via photocoupler cold (as shown below).
• In normal conditions the pin-9 Ac det there must be a voltage of about "4v"
• If the input ac voltage drops, the pin-9 AC voltage det will be changed to "0v", and will cause Mikrokontrol stop working.

 

• Some frequently encountered Ac Det damage to the circuit on the LCD. So that even if the input ac voltage is normal, the voltage on pin-9 Ac Det "zero", because it needs to be tracked damage.
• There is no AC voltage and voltage det st-by will cause Mikrokontrol not work.

 Another example Det circuit Ac

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