Xtreme Power Conversion Corporation
P91, TX91, TX91L, TXVR Service Manual
Page 9
Uninterruptible Power Supply
Figure 4.1 is a flyback converter. When Q1 is on, all rectifier diodes (D1/D2/D3) are on open status and all out-
put capacitors (C1/C2/C3) supply currents to the load. The primary coil of the transformer will become a pure
inductor and the primary current will linearly increase to store energy in the coil. When Q1 is off, primary cur-
rent will stop and all rectifier diodes (D1/D2/D3) will turn to “close” status. It will release the stored energy from
the primary coil of the transformer to the secondary coil to supply loads. At the same time, it will charge output
capacitors including 15V, +12V, +5V, +12V(Fan), and HFPW.
The power of 12V, +5V supplies stable voltage to all kinds of ICs and other devices such as HCT. The
+12V (Fan) is supplied to fans and relays. The HFPW supplies a high frequency power for the switch
(SCR/IGBT) driver and some other drive boards.
4.2 PFC/Booster
N
Q
1
Q
2
U
BUS+
U
BUS-
Utility
Battery
L
1
D
2
D
1
C
1
C
2
N
L
2
Q
3
Q
4
Q
5
Figure 4.2 PFC/Booster
As shown in the Figure 4.2, when Q1/Q2 is on and D1/D2 is off, the current will increase to store energy in
choke(L1/L2). When the Q1/Q2 is off and D1/D2 is on, the choke will release energy. Therefore, we can control
the current in chokes (input current) by regulating the time of Q1/Q2 on and off.
4.3 Inverter
The input of the three level inverter topology is two DC voltages, and the output is an AC voltage, as shown in
the Figure 4.3. When Q1/Q2 is on and Q/Q3 is off, the voltage of the bridge midpoint is +BUS. When Q1/Q2 is off
and Q3/Q4 is on, the voltage of the midpoint bridge is –BUS. We can get any voltage waveform between ±BUS
voltage from LC filter output by regulating the duty cycle of Q1/Q2/Q3/Q4, including sine wave form.
Figure 4.3 Three level inverter bridge