The invention belongs to the technical field of
switching power supply protection, and relates to a power supply detecting and switching device for an
electric energy meter. The power supply detectingand switching device comprises an MCU
chip unit, an auxiliary power circuit unit, a main power circuit unit, a power-off meter-reading battery circuit unit, a
clock battery circuit unit, a DC /
DC circuit unit, a
dummy load circuit unit, a first
voltage detecting circuit unit, a second
voltage detecting circuit unit, a first P-channel
MOSFET circuit unit, and a second P-channel
MOSFET circuit unit.A power supply detects whether the first
voltage detecting circuit unit, the second voltage detecting circuit unit and the DC /
DC circuit unit are powered on. The MCU
chip unit detects the levels of the first voltage detecting circuit unit, the second voltage detecting circuit unit and the DC /
DC circuit unit. When the main power circuit unit is powered off, the power supply automatically switchesto the power-off meter-reading battery circuit unit, and the MCU
chip unit is in a low-
power mode. When the power-off meter-reading battery circuit unit has no power, the power supply automatically switches to the
clock battery circuit unit for power supply.