ON LINE UPS, the main circuit architecture is surge absorption filter circuit, AC to DC converter circuit (AC / DC), DC to AC converter circuit (DC / AC), microprocessor-controlled circuitry, bypass and so on . Its action mode: when utility power work normally, the electricity via surge absorption filter circuit →(AC / DC) →(DC / AC) then convert to AC and output to supply the load and charge the battery simultaneously; Once the microprocessor-controlled circuit detects the electricity is interrupted , the battery will discharge immediately via (DC / AC) ,then convert to AC and output to supply the load. If the microprocessor-controlled circuit detects the UPS breakdown, UPS will turn to be bypass through relay, then the utility power supply the load, and make a noise to inform the user.