5
Press the ON button to power up the optical coupler U1 and U2; powering up the U1
may have the power supply build and powering up the U2 may send a signal of SW-ON
to the control board. After it receives the SWSTAUTS signal (high-level) the CPU will
startup the UPS system.
Press the OFF button and the CPU will send a high-level SHUTDOWN signal in the
battery mode. The reverser on the control panel can make these signals change from
high-level to low-level to decrease the power supply and shutdown the UPS. If the UPS
is in the utility power mode, the utility power can help to build power supply on the
PSDR board. Meanwhile the power supply of the UPS keeps working and the UPS
transfers to bypass mode.
If you press the ON button for more than 0.5 second when the UPS is in line mode, the
UPS will transfer to battery test mode, and the UPS transfers to the line mode after 10
seconds. If you press the ON button again for 0.5 seconds when the UPS is still in the
battery test mode, the UPS will transfer to the line mode. If the utility power suspends
during the battery test mode, the UPS will transfer to the battery mode. If disconnecting
the batteries from the UPS, the UPS will transfer back to the line mode.
Press the ON button for 0.5 second when the UPS is in the battery mode, the buzzer
will stop beeping (1 beep every 4 seconds). Press the ON button another 0.5 second
during that silence, and the beeping of 1-beep-every-4-second will resume.
3.3. PFC/Boost circuit
PFC
:
Power Factor Correction
Because the SCR will be ON only if its positive voltage is higher than its negative
voltage, after the utility power is rectified by the full waveform, the current waveform of
the diode will appear characteristics of high and tine. Thus current waveform not only
contains a great number of harmonics, but also makes the UPS input power factor
lower.
Add a DC/DC PFC after rectifying and correct the input current as a sine wave to make
the input power factor is close to 1.
As shown in the following diagram, when the IGBT is on and the DIODE is off, the
CHOKE will store energy and the current crossing the choke will increase by degrees
with time pass. When the IGBT is off, the choke releases energy and the DIODE is on,
the current of the choke will be descending with time pass. Therefore, we can control
the current waveform of chokes (input current) by regulating the time of IGBT on and off.