Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2001-11-30
2003-07-08
Berhane, Adolf Deneke (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S097000
Reexamination Certificate
active
06590787
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a switching power supply circuit to be provided as a power supply for various electronic apparatus.
Switching power supply circuits employing switching converters such for example as flyback converters and forward converters are widely known. These switching converters form a rectangular waveform in switching operation, and therefore there is a limit to suppression of switching noise. It is also known that because of their operating characteristics, there is a limit to improvement of power conversion efficiency.
Hence, various switching power supply circuits employing resonance type converters have been proposed. A resonance type converter makes it possible to readily obtain high power conversion efficiency, and to achieve low noise because the resonance type converter forms a sinusoidal waveform in switching operation. The resonance type converter has another advantage of being able to be formed by a relatively small number of parts.
FIG. 8
is a circuit diagram showing an example of a related art switching power supply circuit. The fundamental configuration of the power supply circuit shown in the figure has a voltage resonance type converter as a primary-side switching converter.
The power supply circuit shown in the figure generates a rectified and smoothed voltage Ei whose level is equal to that of an alternating input voltage VAC from a commercial alternating-current power by a bridge rectifier circuit Di and a smoothing capacitor Ci.
The voltage resonance type converter for interrupting the rectified and smoothed voltage Ei (direct-current input voltage) inputted thereto includes a switching device Q
1
and employs a single-ended system. The voltage resonance type converter employs a self-excited driving method. In this case, a high voltage bipolar transistor (Bipolar Junction Transistor) is selected as the switching device Q
1
forming the voltage resonance type converter. A primary-side parallel resonant capacitor Cr is connected in parallel with a collector and an emitter of the switching device Q
1
. A clamp diode DD is connected between a base and the emitter of the switching device Q
1
. The parallel resonant capacitor Cr forms a primary-side parallel resonant circuit in conjunction with leakage inductance L
1
obtained in a primary winding N
1
of an isolating converter transformer PIT, whereby operation of the voltage resonance type converter is obtained.
A self-oscillation driving circuit formed by a driving winding NB, a resonant capacitor CB, and a base current limiting resistance RB is connected to the base of the switching device Q
1
. The switching device Q
1
is driven for switching operation by being supplied with a base current based on an oscillating signal generated by the self-oscillation driving circuit. At the start of power supply, the switching device Q
1
is started by a starting current flowing from the rectified and smoothed voltage Ei line to the base of the switching device Q
1
via a starting resistance Rs.
In this case, in addition to the clamp diode DD connected between the base and emitter of the switching device Q
1
, a clamp diode DD
1
is connected between the collector and emitter of the switching device Q
1
.
An orthogonal type control transformer PRT is formed by winging a control winding NC in a winding direction orthogonal to a current detecting winding ND and a driving winding NB. The orthogonal type control transformer PRT is provided to control switching frequency of the primary-side voltage resonance type converter. The structure of the orthogonal type control transformer PRT is a cubic core formed by connecting two table-shaped cores each having four magnetic legs with each other at ends of the magnetic legs. The resonance current detecting winding ND and the driving winding NB are wound around two given magnetic legs of the cubic core in the same winding direction, and the control winding NC is wound around magnetic legs in a direction orthogonal to the resonance current detecting winding ND and the driving winding NB.
An isolating converter transformer PIT (Power Isolation Transformer) is provided to transmit the switching output of the switching converter obtained on the primary side to the secondary side of the switching power supply circuit. The isolating converter transformer PIT is formed by winding the primary winding N
1
and secondary winding N
2
of the isolating converter transformer PIT around an E—E-shaped core in a state of being divided from each other. Also, a gap G is formed in a central magnetic leg of the E—E-shaped core. Thus, loose coupling at a desired coupling coefficient is obtained, and accordingly a saturated state is not readily obtained.
The primary winding N
1
of the isolating converter transformer PIT is connected between the line of the direct-current input voltage and the collector of the switching device Q
1
. The switching device Q
1
performs switching operation on the direct-current input voltage. Thus, the primary winding N
1
is supplied with the switching output of the switching device Q
1
, and thereby generates an alternating voltage having a cycle corresponding to the switching frequency of the switching device Q
1
.
The alternating voltage induced by the primary winding N
1
is generated in the secondary winding N
2
on the secondary side of the isolating converter transformer PIT. In this case, a secondary-side parallel resonant capacitor C
2
is connected in parallel with the secondary winding N
2
. Thereby, leakage inductance L
2
of the secondary winding N
2
and capacitance of the secondary-side parallel resonant capacitor C
2
form a parallel resonant circuit. The parallel resonant circuit converts the alternating voltage induced in the secondary winding N
2
into a resonance voltage. Thus, a voltage resonance operation is obtained on the secondary side.
Thus, the power supply circuit is provided with the parallel resonant circuit to convert switching operation into voltage resonance type operation on the primary side and the parallel resonant circuit to provide voltage resonance operation on the secondary side. The switching converter provided with such resonant circuits on the primary side and the secondary side is referred to as a “complex resonance type switching converter.”
On the secondary side of the isolating converter transformer PIT in this case, an anode of a rectifier diode D
01
is connected to a winding end point of the secondary winding N
2
, and a cathode of the rectifier diode D
01
is connected to a positive electrode terminal of a smoothing capacitor C
01
, thereby forming a half-wave rectifier circuit. The half-wave rectifier circuit provides a secondary-side direct-current output voltage E
01
across the smoothing capacitor C
01
.
In this case, the secondary winding N
2
is provided with a tap, and a half-wave rectifier circuit formed by a rectifier diode D
02
and a smoothing capacitor C
02
is connected to the tap output, as shown in the figure. The half-wave rectifier circuit provides a secondary-side direct-current output voltage E
02
that is lower than the secondary-side direct-current output voltage E
01
. Incidentally, the secondary-side direct-current output voltage E
01
is 135 V, and the secondary-side direct-current output voltage E
02
is 15 V, for example.
The secondary-side direct-current output voltages E
01
and E
02
are each supplied to a required load circuit. The secondary-side direct-current output voltage E
01
is outputted from a branch point as a detection voltage for a control circuit
1
, and the secondary-side direct-current output voltage E
02
is outputted from a branch point as operating power for the control circuit
1
.
The control circuit
1
supplies the control winding NC of the orthogonal type control transformer PRT with a direct current that is variably changed according to the level of the secondary-side direct-current output voltage E
01
as a control current. In response to the change in the level of the control current flowing through the control wind
Berhane Adolf Deneke
Maioli Jay H.
Sony Corporation
LandOfFree
Wide range zero voltage switching resonance type converter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wide range zero voltage switching resonance type converter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wide range zero voltage switching resonance type converter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3085257