Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2001-07-09
2002-04-09
Berhane, Adolf Deneke (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
Reexamination Certificate
active
06370041
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a switching power supply circuit suitable as a power supply for a television receiver, for example.
A color television receiver having a cathode-ray tube (hereinafter abbreviated to a CRT) for image display, for example, generally uses a power supply circuit formed by a horizontal deflection circuit for deflecting an electron beam emitted from an electron gun within the CRT in a horizontal direction and a switching power supply of the soft switching type formed by a current resonance type converter.
FIG. 9
shows configuration of a horizontal deflection circuit and its peripheral circuit provided in a television receiver.
The switching power supply
10
shown in
FIG. 9
is a DC-to-DC converter for performing switching operation on a direct-current voltage inputted thereto and converting the direct-current voltage into a direct-current voltage having a specified voltage level for output.
A rectifying and smoothing circuit is provided before the switching power supply
10
. The rectifying and smoothing circuit rectifies and smoothes a commercial alternating-current power VAC to thereby provide a direct-current voltage Ei. The direct-current voltage Ei is then inputted to the switching power supply
10
.
The switching power supply
10
outputs a direct-current output voltage E
01
converted into a specified voltage level and the like.
In this case, the direct-current output voltage E
01
is a voltage for driving the horizontal deflection circuit of the television receiver, and is 135 V, for example.
A horizontal output circuit
20
generates a horizontal deflection current IDY for scanning an electron beam emitted from an electron gun in a CRT in a horizontal direction, and also generates a flyback pulse for generating a high voltage in a high-voltage generating circuit
40
, which will be described later.
Thus, a pulse voltage in synchronism with a horizontal synchronizing signal fH of a video signal is inputted from a horizontal driving circuit not shown in the figure to a base of a horizontal output transistor Q
11
of the horizontal output circuit
20
.
A collector of the horizontal output transistor Q
11
is connected to a secondary-side output terminal E
01
of the switching power supply
10
via a primary-side winding N
11
of a flyback transformer FBT. An emitter of the horizontal output transistor Q
11
is grounded.
A damper diode D
11
, a horizontal flyback line capacitor Cr
11
, and a series connection circuit formed by a horizontal deflection yoke H·DY, a horizontal line correction coil HLC, and an S-shape correction capacitor CS
1
are each connected in parallel with the collector and emitter of the horizontal output transistor Q
11
.
In the horizontal output circuit
20
thus formed, capacitance of the horizontal flyback line capacitor Cr
11
and a leakage inductance component of the primary-side winding N
11
of the flyback transformer FBT form a voltage resonance type converter.
The pulse voltage inputted from the horizontal driving circuit not shown in the figure causes the horizontal output transistor Q
11
to perform switching operation, whereby a horizontal deflection current IDY having a sawtooth waveform flows through the horizontal deflection yoke H·DY. During the off period of the horizontal output transistor Q
11
, a relatively high pulse voltage V
11
is generated across the horizontal flyback line capacitor Cr
11
as a result of resonance operation by inductance LDY of the horizontal deflection yoke H·DY and the capacitance of the horizontal flyback line capacitor Cr
11
and the effect of the damper diode D
11
.
Incidentally, the horizontal line correction coil HLC and the S-shape correction capacitor CS
1
correct the horizontal deflection current IDY, for example, to thereby correct distortion of an image displayed on the screen of the CRT.
The high-voltage generating circuit
40
enclosed by alternate long and short dashed lines comprises the flyback transformer FBT and a high-voltage rectifying and smoothing circuit, for example. The high-voltage generating circuit
40
steps up the flyback pulse voltage V
11
generated in the horizontal output circuit
20
to thereby generate a high voltage whose level is equivalent to that of an anode voltage of the CRT.
The primary-side winding N
11
is wound on the primary side of the flyback transformer FBT, and five step-up windings NHV
1
, NHV
2
, NHV
3
, NHV
4
, and NHV
5
are divided and wound by slit winding or layer winding on the secondary side of the flyback transformer FBT.
Also, tertiary windings N
12
and N
13
are wound in a state of being closely coupled to the primary-side winding N
11
on the primary side of the flyback transformer FBT.
In this case, the step-up windings NHV
1
to NHV
5
are wound in a winding direction such that the step-up windings NHV
1
to NHV
5
are of opposite polarity from the primary-side winding N
11
. The tertiary windings N
12
and N
13
are wound such that the tertiary windings N
12
and N
13
are of the same polarity as the primary-side winding N
11
.
A starting point of the primary-side winding N
11
is connected to the secondary-side output terminal E
01
of the switching power supply
10
, while an ending point of the primary-side winding N
11
is connected to the collector of the horizontal output transistor Q
11
.
Ending points of the step-up windings NHV
1
to NHV
5
are connected with anodes of high-voltage rectifier diodes DHV
1
, DHV
2
, DHV
3
, DHV
4
, and DHV
5
, respectively.
A cathode of the high-voltage rectifier diode DHV
1
is connected to a positive terminal of a high-voltage capacitor CHV, and cathodes of the high-voltage rectifier diodes DHV
2
to DHV
5
are connected to starting points of the step-up windings NHV
1
to NHV
4
, respectively.
Specifically, a half-wave rectifier circuit of the so-called multi-singular type is formed on the secondary side of the flyback transformer FBT by series connection of five half-wave rectifier circuits: the step-up winding NHV
1
and the high-voltage rectifier diode DHV
1
; the step-up winding NHV
2
and the high-voltage rectifier diode DHV
2
; the step-up winding NHV
3
and the high-voltage rectifier diode DHV
3
; the step-up winding NHV
4
and the high-voltage rectifier diode DHV
4
; and the step-up winding NHV
5
and the high-voltage rectifier diode DHV
5
.
Thus, on the secondary side of the flyback transformer FBT, the five half-wave rectifier circuits rectify currents induced in the step-up windings NHV
1
to NHV
5
and store the resulting currents in the high-voltage capacitor CHV, whereby a high direct-current voltage EHV whose level is equivalent to five times the voltages induced in the step-up windings NHV
1
to NHV
5
is obtained across the high-voltage capacitor CHV. The high direct-current voltage EHV obtained across the high-voltage capacitor CHV is used as the anode voltage of the CRT, for example.
Incidentally, an induced voltage stepped up to 6 KV is obtained in each of the step-up windings NHV
1
to NHV
5
, and an anode voltage of 30 KV is obtained as the high direct-current voltage EHV.
The primary-side winding N
11
of the flyback transformer FBT is provided with a tap. A half-wave rectifying and smoothing circuit formed by a rectifier diode D
03
and a smoothing capacitor C
03
rectifies and smoothes a positive pulse voltage obtained from the tap to thereby supply a direct-current output voltage E
03
from across the smoothing capacitor C
03
. The direct-current output voltage E
03
has a voltage level of 200 V, for example, and is supplied to a cathode of the CRT via a video signal amplifier not shown in the figure.
A rectifying and smoothing circuit formed by a rectifier diode D
06
and a smoothing capacitor C
06
and a rectifying and smoothing circuit formed by a rectifier diode D
07
and a smoothing capacitor C
07
rectify and smooth a negative pulse voltage obtained from the tertiary winding N
12
wound on the primary side of the flyback transformer FBT, and thereby supply direct-current output voltages E
06
and E
07
from
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