AP16098
UPS Main Control
System Overview
Application Note
7
V1.0, 2007-03
To eliminate the common noise, the input power is first filtered by an EMI filter which is
connected to tow fuses. Afterwards the power flows into the passive power factor
correction circuit in order to ensure the input current shape quality.
After reduction of voltage by an autotransformer, the input line voltage is rectified into DC
voltage. The DC-bus voltage is then filtered and regulated by capacitors with a resistor in
series which can restrain the inrush current. A relay is placed in parallel with the resistor
and it will be closed to shorten this resistor when the DC-bus voltage reaches a certain
value.
The battery module is connected with the DC-bus capacitors through a diode. If input line
power blackout happens, the battery module will be switched to offer power to the inverter
in order to keep the power uninterrupted.
The full-bridge inverter is utilized, whose output voltage is boosted by an isolating
transformer and then filtered by the circuit consisting of inductor and capacitors. The
leakage inductance of the transformer is adopted to filter out the high frequency and
difference voltage. The output voltage of the inverter also provides power to the battery
charger circuit. In “line” mode the charger circuit will receive the command to run from the
control board, but in “bat” mode it always remains off.
A TRIAC is connected with the bypass relay via a switch. When overload or other fault
occurs, the system will automatically switch to bypass mode so that the whole system as
well as the load has got protection.
Figure 3 illustrates the topology utilized in this UPS reference design.
Figure 3
UPS Topology
