Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2000-09-21
2001-10-09
Riley, Shawn (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C323S207000
Reexamination Certificate
active
06301129
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a switching power supply circuit which includes a power factor improvement circuit.
The applicant of the present invention has proposed various power supply circuits which include a resonance type converter on the primary side. Also various power supply circuits wherein a power factor improvement circuit for improving the power factor is provided for a resonance type converter have been proposed by the applicant of the present invention.
FIG. 10
is a circuit diagram showing an example of a switching power supply circuit constructed in accordance with the invention having been applied for patent by the present applicant. The power supply circuit is constructed such that a power factor improvement circuit for improving the power factor is provided for a self-excited current resonance type switching converter.
The power supply circuit shown in
FIG. 10
includes a bridge rectification circuit Di for full wave rectifying a commercial ac power supply AC. In this instance, a rectification output obtained by rectification by the bridge rectification circuit Di is charged into a smoothing capacitor Ci through a power factor improvement circuit
20
, and a rectified smoothed voltage Ei corresponding to the level equal to the ac input voltage VAC is obtained across the smoothing capacitor Ci.
An inrush current limiting resistor Ri is inserted in the rectification current path of the rectification smoothing circuit (Di, Ci) so that inrush current to flow into the smoothing capacitor, for example, when supply of power is started, may be suppressed.
In the power factor improvement circuit
20
shown in
FIG. 10
, a filter choke coil LN—high speed recovery type diode D
1
—choke coil LS connected in series are inserted between a positive output terminal of the bridge rectification circuit Di and a positive terminal of the smoothing capacitor Ci.
A filter capacitor CN is interposed between the anode side of the high speed recovery type diode D
1
and the positive terminal of the smoothing capacitor Ci to form a low-pass filter of a normal mode together with the filter choke coil LN.
In the power factor improvement circuit
20
, a terminal of a primary side series resonance circuit which is hereinafter described is connected to a connection point between the cathode of the high speed recovery type diode D
1
and the choke coil LS so that a switching output obtained by the dc resonance circuit may be fed back.
It is to be noted that a power factor improvement operation of the power factor improvement circuit
20
is hereinafter described.
The power supply circuit includes a self-excited current resonance type converter which uses the rectified smoothed voltage Ei which is a voltage across the smoothing capacitor Ci as operating current.
The current resonance type switching converter includes a pair of switching elements Q
1
and Q
2
formed from bipolar transistors, connected in a half bridge connection as seen in FIG.
10
and interposed between the positive electrode side connection point of the smoothing capacitor Ci and the ground.
Starting resistors RS
1
and RS
2
are interposed between the collector and the base of the switching elements Q
1
and Q
2
, respectively. A pair of resistors RB
1
and RB
2
connected to the base of the switching elements Q
1
and Q
2
set base current (drive current) of the switching elements Q
1
and Q
2
. A pair of clamp diodes DD
1
and DD
2
are interposed between the base and the emitter of the switching elements Q
1
and Q
2
, respectively. The clamp diodes DD
1
and DD
2
form current paths for clamp current which flows between the base and the emitter of the switching elements Q
1
and Q
2
within periods within which the switching elements Q
1
and Q
2
are off.
A pair of resonance capacitors CB
1
and CB
2
form series resonance circuits for self-excited oscillation (self-excited oscillation driving circuits) together with drive windings NB
1
and NB
2
of a drive transformer PRT (Power Regulating Transformer), which are described subsequently, and determine switching frequencies of the switching elements Q
1
and Q
2
.
The drive transformer PRT is provided to drive the switching elements Q
1
and Q
2
and variably control the switching frequencies to perform constant voltage control. The drive transformer PRT shown in
FIG. 10
is formed as an orthogonal saturable reactor on which the drive windings NB
1
and NB
2
and a resonance current detection wiring ND are wound and a control winding NC is wound in a direction orthogonal to the windings.
An end of the drive winding NB
1
of the drive transformer PRT is connected to the base of the switching element Q
1
through a series connection of the resistor RB
1
and the resonance capacitor CB
1
, and the other end of the drive winding NB
1
is connected to the emitter of the switching element Q
1
. An end of the drive winding NB
2
is connected to the ground, and the other end of the drive winding NB
2
is connected to the base of the switching element Q
2
through a series connection of the resistor RB
2
and the resonance capacitor CB
2
. The drive winding NB
1
and the drive winding NB
2
are wound such that they may generate voltages having the polarities opposite to each other.
An insulation converter transformer PIT (Power Isolation Transformer) transmits switching outputs of the switching elements Q
1
and Q
2
to the secondary side. An end of the primary winding N
1
of the insulation converter transformer PIT is connected to a connection point (switching output point) between the emitter of the switching element Q
1
and the collector of the switching element Q
2
through the resonance current detection wiring ND so that a switching output may be obtained.
The other end of the primary winding N
1
is connected to a connection point between the cathode of the high speed recovery type diode D
1
in the power factor improvement circuit
20
and the choke coil LS through a series resonance capacitor C
1
.
In this instance, the series resonance capacitor C
1
and the primary winding N
1
are connected in series. Thus, a primary side series resonance circuit for making operation of the switching converter operation of the current resonance type is formed from a capacitance of the series resonance capacitor C
1
and a leakage inductance component of the insulating converter transformer PIT including the primary winding N
1
(series resonance winding).
On the secondary side of the insulating converter transformer PIT shown in
FIG. 10
, a center tap is provided for the secondary winding N
2
, and rectification diodes D
01
, D
02
, D
03
and D
04
and smoothing capacitors C
01
and C
02
are connected in such a manner as seen in FIG.
10
. By the connection, two sets of full wave rectification circuits including a set of the [rectification diodes D
01
and D
02
and smoothing capacitor C
01
] and another set of the [rectification diodes D
03
and D
04
and smoothing capacitor C
02
] are provided. The full-wave rectification circuit formed from the [rectification diodes D
01
and D
02
and smoothing capacitor C
01
] produces a dc output voltage E
01
, and the full-wave rectification circuit formed from the [rectification diodes D
03
and D
04
and smoothing capacitor C
02
] produces another dc output voltage E
02
.
It is to be noted that, in this instance, the dc output voltage E
01
and the dc output voltage E
02
are branched and inputted also to a control circuit
1
. The control circuit
1
utilizes the dc output voltage E
01
as a detection voltage and utilizes the dc output voltage E
02
as an operation power supply to the control circuit
1
.
The control circuit
1
supplies dc current whose level is varied, for example, in response to the level of the dc output voltage E
01
on the secondary side as control current to the control winding NC of the drive transformer PRT to perform constant voltage control in such a manner as hereinafter described.
In a switching operation of the power supply circuit hav
Frommer William S.
Frommer Lawrence & Haug LLP.
Riley Shawn
Sony Corporation
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