Acer AL2016, Service Manual

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Acer Service Manual
Chapter 3- CIRCUIT THEORY
1. Functional Block Diagram
2. Electronic Circuit Theory
2.1 Switching Mode Power Supply
2.1.1 AC Current Input Circuit
P801 is a connector for connecting AC Power. F801 is a fuse to protect all the circuit. AC input voltage
is from 100V to 240V. R801 and R802 joined between two inputting main circuit to prevent man from
shock. L801 is used to clear up low frequency wave. C801 and C802 are used to discharge the waves
that L801 produced. High frequency waves are damped by C801 and C802. D801 is a rectifier which
composed of 4 build-in diodes, it inverts AC to DC.
2.1.2 High Voltage to Low Voltage Control Circuit
C804 is used to smooth the waveform from rectifier. IC802 is a highly integrated PWM controller,
which control the power MOSFET Q804. When rectified DC high voltage is applied to the DRAIN pin
during start-up, the MOSFET is off initially, and the capacitor C807 be charged through D802,R803
and the HV pin of IC802,when the voltage VCC reaches the threshold level 12.8V,IC 802 start up and
create a PWM waveform to control the power MOSFET, then energy is transferred to secondary
terminal through the transformer T801,the auxiliary voltage 12V and the output voltage 18V be
created ,the auxiliary voltage supply a continue current to IC802,the level of out put voltage is
feedback to FB pin of IC802 through R823,R837,R822,IC803 and IC801 witch control the duty of the
PWM waveform, then all the convert circuit go to a stable operating station.
R805 R806 R835 ZD801 ZD806 and Q801 formed a under input voltage protection circuit , only the
input AC voltage over the threshold level approximately 63V AC, the switch Q801 can be on and then
the auxiliary voltage can supply a continue current to IC802;R808,R807,R836,R812,R815,R839,D806
and Q805 formed a over line current protection circuit witch limited the input power under
approximately 63W. ZD802 will be on when the output voltage is too high or the feedback circuit open,
the current will drive transistor Q805 open through R830, D814 and made IC802 off; the high voltage
spike created by transformer’s primary winding during the transistor turn off will be consumed through
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