Teclast X21, Руководство по обслуживанию

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Above, I is about 200 milliampere. The reason why we design like this is that USB jack of some
REF
computers (such as laptop computer) cannot provide large current to charge battery.
3.2.7 Low voltage detecting circuit
1. Function of low voltage detecting circuit is that when input voltage of he player is detected to be
lower than a certain voltage value, the player turns off. Low voltage detecting circuit schematic diagram
is shown in the figure 3.2.7.1:
U5
S80829CNNB/S1000N29-N4T1/R3111Q291AT1 S
RST
1
VDD
2
NC
3
VSS
4
C15
102*
R18 33K
R10
100K
R15
470K
R24
100K
Q4
MMST3906
P_GND
P_VDD
P_GND
VCC33
P_GND
P_GND
EN
Figure 3.2.7.1 Low voltage detecting circuit schematic diagram
2. Working principle: low voltage detecting ciorcuit is fulfilled by IC S80829CNNB and PNP triode
Q4. S80829CNNB is high precision voltage detector detect valve value is 2.9V and precision is +2 .
P_VDD is he input voltage of the player, when P_VDD is lower than 2.9V, RST pin of IC outputs low level,
pin triode Q4 is saturated on, control level output is low level which cuts off the power pf the player to
power off.
3.2.8 Battery protection circuit
1. Battery protection board is installed on lithium battery and used to protect lithium battery from
being damaged by short circuit, over discharge and over charge. Lithium battery and battery protection
board are all lithium battery core components by us. Circuit schematic diagram of battery protection
board is shown in the figure 3.2.8.1:
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figure 3.2.8.1 Battery protection circuit diagram