Service manual

The MOSFETs turn on /off in turn, can prevent the saturation of the transformer and damage of
the circuit.
Like the AC/DC converter, the DC/DC converter output regulated±350 Vdc, ±360 Vdc,±370 Vdc
to the DC –BUS when the UPS output voltage is set to 220Vac, 230V, 240Vac respectively.
5.2.3 Inverter
The inverter converse the DC power from DC BUS into the AC output to supply the load. A half
bridge topology employed, Figure 5.2.3.1 shows a diagram of inverter in 1/2/3k product.
Figure 5.2.3.1 Schematics for inverter
The half bridge inverter comprise a pair of complement switching device, IGBT, a free wheel
diode parallel with each IGBT, forming a switching leg, a driving circuit for each IGBT, a LC filter,
and the controller. In the real circuit, an IGBT with co-pack diode is used to simplify circuit and
achieve minimize stray parameter,
When the positive IGBT is turned on, The output of half bridge is equal to Positive DC-BUS
voltage, when the positive IGBT is turned off, either the negative IGBT is turn on or the negative
free-wheel diode is active, the output of the switching leg is negative DC-BUS, so by change the
duty cycle, average of output of the switching leg can vary from +BUS voltage to –BUS voltage,
20