Acer H15AAX, Руководство по обслуживанию

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Circuit Description
H15AAX (AL502)
Page 1
1. Audio circuit (Circuit diagrams Main PWB)
1.1 Audio input
The audio signal input received from the audio input terminal (JK011) is applied to the amplifier I001 of 4 (L-
CH) and 9 (R-CH) through the low-pass filter consisting of R040, R041, R042, R043, C040 and C041.
In this amplifier, controls of Volume and mute are conducted. The audio signal controlled at the pin 6 determines
the attenuation of output of the amplifiers. Since then, the signal is output to the jack P003.
1.2 Audio output
The audio signal is output from P002 output terminal of the Audio block to the internal speaker system.
2. Power supply (Circuit daigrams MAIN PWB)
2.1 Line filter consists of C801, T801, C802, C803, C804. It eliminates high frequency interference to meet EMI’s
requirement.
2.2 Rec & Filter :
Bridge diode D801 converts AC source into pulsed DC. This pulsed DC is smoothed and filtered by C805.
R802 is an NTC ( negative thermal coefficient ) resistor, used to reduce inrush current to be within safe range.
2.3 Powe r tran sforme r :
T802 converts energy for square wave from power source C805 to secondary side to ge12V and +5V.
2.4 Output :
The square wave from T802 is rectified by D809, D810, then filtered by C817, C822 to ge12V and
+5V respectively.
2.4.1 A 5V power supply for LCD module, CPU and logic i s generated from the p ower source.
2.4.2 I308 : 3-terminal regulator
A 3.3V power supp ly for I306 analog is generated from the 5V source.
2.4.3 I308 : 3-terminal regulator
A 3.3V power suppl y for I306 digital is generated from the 5V source.
Q302, Q303 ON/OFF control for LCD Module
ON/OFF co ntrol is performed for power ON/OFF and also for t he power saving sequence.
2.5 Driv er :
Q803 drive T802 from PWM control of I801 for p ower converted.
2.6 FB :
Negative feedback CKT consists of photo coupler I802 and adjustable regulator I803. It can maintain output
vo5V and +12V at a stable level.
2.7 PWM :
2.7.1
Start
: When power is turned on, Q801 conducts due to bias from C805 and R805,R803. C807 is charged a 16
volt and a starting current about 0.3mA to pin 7 of I801. I801 starts to oscillate and outputs a pulse train
through pin 6 to drive Q803.
2.7.2
OPP
: When Q803 turns on, C805 supplies a linearly increasing triangle current through the primary induc
tance of T802 to the driver Q803, once the peak value of this current multiplied by R811 exceeds1 volt, pulse
train will be shut down immediately to protect Q803, T802 from being burned out.
2.7.3
Regulation
: If output v5V goes up, the R terminal of I803 gets more bias, accordingly photo transis
tor and photo diode flows more current. The voltage of pin 2 goes up too, making the pulse width of pin 6 to
become narrower. So the output v5V will be pulled down to a stable value.