Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2000-06-20
2001-09-18
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S071000, C363S134000
Reexamination Certificate
active
06292377
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a power supply device comprising a plurality of resonance type switching converters connected in parallel.
2. Prior Art
Current resonance type switching converters are known. A current resonance type switching converter is realized by adding a resonance circuit to a switching transistor for the purpose of switching voltages. Current resonance type switching converters provide a major advantage that the electric current flowing through the primary side of the transformer shows a sinusoidal waveform to reduce the current loss and the switching noise due to switching operations because of the resonance circuit added to it.
Power supply devices realized by connecting a plurality of such current resonance type switching converters in parallel are also known. It is possible to supply a large power to a load when a plurality of current resonance type switching converters are connected in parallel.
FIG. 1
of the accompanying drawings shows a schematic circuit diagram of a known power supply device realized by connecting a pair of current resonance type switching converters.
The known power supply device
100
of
FIG. 1
comprises an AC input terminal
102
, a power factor improving circuit (P. F. C.)
103
, a first current resonance type switching converter
104
, a second current resonance type switching converter
105
, a frequency control circuit
106
and a feedback circuit
107
.
Typically a commercial AC voltage may be applied to the known power supply device
100
by way of the AC input terminal
102
. The applied AC voltage is then fed to the power factor improving circuit
103
. After boosting the applied AC voltage and improving its power factor, the power factor improving circuit
103
rectifies the AC and outputs a DC input voltage (Vin) that may be for instance as high as 380(V).
The DC input voltage (Vin) is then fed to the first current resonance type switching converter
104
and the second current resonance type switching converter
105
. Note that, hereinafter, the first current resonance type switching converter
104
and the second current resonance type switching converter
105
are referred to simply as the first converter
104
and the second converter
105
respectively.
The first converter
104
is controlled for its switching frequency by a frequency control signal from frequency control circuit
106
and converts the DC input voltage (Vin) it receives into a DC output voltage (Vout) that is stabilized to show a predetermined voltage value. Similarly, the second converter
105
is also controlled for its switching frequency by a frequency control signal from the frequency control circuit
106
and converts the DC input voltage (Vin) it receives into a DC voltage (Vout) that is stabilized to show a predetermined voltage value. The output terminal of the first converter
104
and that of the second converter
105
are connected in parallel and are used to supply the load
101
with their respective DC outputs (Vout).
The first converter
104
is provided with a DC input terminal
111
and the DC input voltage (Vin) is applied to it by way of the input terminal
111
. The first converter
104
is also provided with a control signal input terminal
112
and a frequency control signal is applied to it from the frequency control circuit
106
by way of the control signal input terminal
112
.
The first converter
104
has a first switching transistor
113
and a second switching transistor
114
. The collector of the first switching transistor
113
is connected to said DC input terminal
111
. The collector of the second switching transistor
114
is connected to the emitter of the first switching transistor
113
, which emitter is then grounded.
The first converter
104
also has a driving transformer
115
for driving the first switching transistor
113
and the second switching transistor
114
.
The driving transformer
115
includes a primary winding
115
a
and a pair of secondary windings
115
b
,
115
c
. The primary winding
115
a
of the driving transformer
115
is fed with the frequency control signal sent from the frequency control circuit
106
by way of the control signal input terminal
112
. The two secondary windings
115
b
,
115
c
of the driving transformer
115
are wound in opposite directions. One of the secondary windings, or the secondary winding
115
b
, is connected at an end thereof to the base of the first switching transistor
113
by way of resistor
116
and at the other end thereof to the emitter of the switching transistor
113
. On the other hand, the other secondary winding, or the secondary winding
115
c
, is connected at an end thereof to the base of the second switching transistor
114
and at the other end thereof to the emitter of the second switching transistor
114
.
The first switching transistor
113
and the second switching transistor
114
connected respectively to the two secondary windings
115
b
,
115
c
of the driving transformer
115
that are wound in opposite directions are complementarily switched according to the frequency control signal input to the primary winding
115
a
of the driving transformer
115
.
The first converter
104
includes an insulating transformer
117
, a resonance capacitor
118
arranged at the primary side of the insulating transformer
117
and first and second rectifier diodes
121
and
122
arranged at the secondary side of the insulating transformer
117
.
The primary winding
117
a
of the insulating transformer
117
is connected at an end thereof to the emitter of the first switching transistor
113
and grounded at the other end thereof by way of the resonance capacitor
118
and resistor
120
. The secondary winding
117
b
of the insulating transformer
117
is connected at an end thereof to the anode of the first rectifier diode
121
and at the other end thereof to the anode of the second rectifier diode
122
. The cathode of the first rectifier diode
121
and that of the second rectifier diode
122
are connected to positive side output terminal
123
, whereas negative side output terminal
124
is connected to the middle point of the secondary winding
117
b
of the insulating transformer
117
.
When the first switching transistor
113
and the second switching transistor
114
of the first converter
104
having the above described configuration are complementarily and repeatedly turned on and off according to the frequency control signal from the frequency control circuit
106
, a voltage having a rectangular waveform is applied to the opposite ends of the primary winding
117
a
of the insulating transformer
117
. As a voltage having a rectangular waveform is applied, a resonance current having a sinusoidal waveform flows through the primary winding
117
a
as a concerted effect of the capacitance of the resonance capacitor
118
and the inductance of the insulating transformer
117
. It should be noted that a resonance current flows through the primary winding
117
a
of the insulating transformer
117
only when such a voltage is applied to the opposite ends of thereof. As a resonance current flows through the primary winding
117
a
, the energy applied to the primary winding
117
a
is transferred to the secondary winding
117
b
to cause an electric current to flow therethrough. The electric current flowing through the secondary winding
117
b
is rectified by the two rectifier diodes
121
,
122
and output from the positive side output terminal
123
.
Load
101
is connected between the positive side output terminal
123
and the negative side output terminal
124
of the first converter
104
having the above described configuration. Additionally, a smoothing capacitor
125
is arranged between the positive side output terminal
123
and the negative side output terminal
124
so that a stabilized DC output current (Vout) is fed to the load
101
from the first converter
104
with a predetermined voltage value.
The second converter
105
has a configuration same as that of
Kananen Ronald P.
Patel Rajnikant B.
Rader Fishman & Grauer
Sony Corporation
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