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Figure1-15
External power overvoltage protection module
2. DC/DC power module
The DC/DC power module generates 4.4V main power necessary for the operation
of the whole machine. It also fulfills the constant current charging function. The
maximum output current is 830mA. We mainly use the PWM control chip (U302)
and the switch transistor (Q301) to complete the second-time switch power circuit.
It is the switch power supply that converts the external power into 4.4V.
See Figure 1-17
15
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