Load Detection Circuit - FSP Technology EP450 series Specifications

11 Load Detection Circuit

Load detection circuit is shown on Figure S-9. The output current is detected by current
transformer CT1AX. It lowers 1000 times of output current for CPU detection. The current
signal generated from CT1AX flows through a full-bridge rectifier and R3AX to convert to
a voltage signal (0~ 5 Volts). Then CPU can receive output current value of the UPS.
11.1 At line/ boost/ buck mode: The current value multiplies output voltage to get output
VA value.
11.2 At battery mode: Because the power factor of step wave is approximately equal to 1,
the current value multiplies 120V (230V) output voltage to get output Watt value.
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Figure S-9 Load Detection Circuit
Rev. A