Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2002-08-23
2003-12-02
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S098000
Reexamination Certificate
active
06657873
ABSTRACT:
BACKGROUND
FIG. 5 is a diagram showing a conventional switching power supply circuit described in “High-Frequency Isolation UPS with Novel SMR” (IECOM '93, pp. 1258-1263, (1993)). Such a conventional switching power supply circuit includes a first series circuit including diodes D
1
and D
2
connected in series, a second series circuit including MOSFETs Q
1
and Q
2
connected in series, and a third series circuit including MOSFETs Q
3
and Q
4
connected in series. The conventional switching power supply circuit also includes a snubber circuit SN connected in parallel with the first through third series circuits.
A first AC input terminal U is connected to the common connection point of the diodes D
1
and D
2
. A primary winding section P
1
of a transformer T
1
having center taps is connected to the common connection point of the MOSFETs Q
1
and Q
2
. The other primary winding section P
2
of the transformer T
1
is connected to the common connection point of the MOSFETs Q
3
and Q
4
. The center tap between the primary winding sections P
1
and P
2
of the transformer T
1
is connected to a second AC input terminal V.
The secondary winding sections S
1
and S
2
of the transformer T
1
are connected to an end of a capacitor C
5
via diodes D
3
and D
4
, respectively. The center tap between the secondary winding sections S
1
and S
2
of the transformer T
1
is connected to the other end of the capacitor C
5
. DC output terminals P and N are connected to the capacitor C
5
.
When the transformer T
1
(the primary winding sections P
1
and P
2
) is short circuited by switching ON the MOSFETs Q
1
and Q
3
while the AC input voltage is positive, the current of a reactor L
1
increases. When the MOSFET Q
3
is switched OFF in the state described above, the reactor current flows through the primary winding section P
1
from the MOSFET Q
1
, feeding electric power to the capacitor C
5
via the secondary winding section S
1
and the diode D
3
.
When the transformer is short circuited again by switching ON the MOSFET Q
3
, the reactor current increases. When the MOSFET Q
1
is switched OFF subsequently, the reactor current flows through the MOSFET Q
3
. The reactor current flowing through the MOSFET Q
3
excites the primary winding section P
2
of the transformer T
1
, and electric power is fed to the capacitor C
5
via the secondary winding section S
2
and the diode D
4
.
By repeating the operations described above at a high frequency, the AC input voltage is insulated and converted to DC electric power by the transformer T
1
. The insulated and converted DC electric power is output via the diodes D
3
, D
4
and the capacitor C
5
. When the AC input voltage is negative, the conventional switching power supply operates in the same manner as described above by switching ON and OFF the MOSFETs Q
2
and Q
4
.
The conventional switching power supply circuit employs four MOSFETs Q
1
through Q
4
, a reactor L
1
, and a snubber circuit SN. Since it is necessary for the conventional switching power supply circuit to incorporate four driving circuits, each driving any of the MOSFETs Q
1
through Q
4
, the size of the conventional switching power supply circuit is large and the cost thereof is high. Since there exits certain time points where the single-phase AC input voltage is zero, the energy fed to the load is interrupted, causing large ripple voltages on the load. For obviating this problem, it is necessary for the capacitor C
5
on the load side to have a sufficiently large capacity. Therefore, the size of the conventional switching power supply circuit is further enlarged and the cost thereof increased even further.
Accordingly, there is a need for a switching power supply circuit that at least reduces the capacity of the capacitor on the load side to reduce its size, weight, and cost. The present application addresses this need.
SUMMARY OF THE INVENTION
The present invention relates to a switching power supply circuit. The switching power supply circuit can have a transformer, a pair of diodes, which can form a first circuit, a pair of switching devices, which can form a second circuit, a pair of capacitors, which can form a third circuit, a snubber capacitor, and first and second AC input terminals.
The transformer can have a primary winding with a center tap and a secondary winding. The pair of diodes are connected in series, as are the pair of switching devices and the pair of the capacitors. The first AC input terminal is connected to both diodes or the common connection point of the two diodes. The second AC input terminal is connected to the center tap of the primary winding. The snubber capacitor, the pair of diodes, the pair of switching devices, and the pair of capacitors are connected in parallel. One end of the primary winding is connected to both switching devices or the common connection point of the switching devices. The other end of the primary winding is connected to both capacitors or the common connection point of the pair of capacitors.
The switching power supply circuit can further include a rectifying circuit, which can be connected to the secondary winding of the transformer, and a switching means for converting a single-phase AC input voltage to a high-frequency AC voltage. The transformer can insulate the high-frequency AC voltage. The rectifying circuit can rectify the insulated high-frequency AC voltage to feed DC electric power to a load.
The switching power supply circuit can further include at least one capacitor connected in parallel with at least one of the switching devices, wherein the at least one capacitor allows at least one of the switching devices to execute a zero-voltage switching. The switching power supply circuit can adjust an ON-OFF duty ratio of one of the switching devices to regulate the current of the AC input voltage and the operating frequency of the other of the switching devices to regulate the DC electric power.
REFERENCES:
patent: 4217632 (1980-08-01), Bardos et al.
patent: 4525774 (1985-06-01), Kino et al.
patent: 4663699 (1987-05-01), Wilkinson
patent: 5081570 (1992-01-01), Chibani et al.
patent: 6208529 (2001-03-01), Davidson
patent: 6215683 (2001-04-01), Mao
“High Frequency Isolation UPS with Novel SMR”; Yamada et al.; IEEE Publication 0-7803-0891-3/93; dated 1993; pp. 1258-1263.
Fuji Electric & Co., Ltd.
Patel Rajnikant B.
Rossi & Associates
LandOfFree
Switching power supply circuit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Switching power supply circuit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Switching power supply circuit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3158985