Service manual

DC-BUS capacitor can be controlled, therefore the voltage of the DC BUS can be controlled, at
the same time the waveform of the current can also be controlled to track the input voltage
waveform, implement the power factor correction.
The P.F.C. output voltage, i.e. the DC BUS voltage, will be regulated at ±350 Vdc, ±360 Vdc,
and ±370 Vdc when the UPS output voltage is set to 220Vac, 230V, and 240Vac respectively.
5.2.2 DC/DC converter (Battery Booster)
In case the AC mains interrupt or being out of tolerance range, the global controller stop the PFC
converter and start the DC/DC converter to converse the DC power from the battery to maintain
the DC-BUS voltage, therefore maintain the output power supply to the load.
Figure 5.2.2.1 DC/DC Converter
The DC/DC converter employed a push-pull power topology, the driving circuit, and the controller.
The controller is major comprise ASIC UC3525 and auxiliary circuit.
The DC/DC converter controller drive a pair of switching component, MosFET used here, turn on
in turns, the switch frequency goes above 40kHz. Either of the MosFET is turned on, there will be
power from the Battery transfer to the secondary side of the transformer to charging the DC-BUS.
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