Rectifying/smoothing circuit and double-ended converter

Details Rectifying/smoothing circuit and double-ended converter Rectifying/smoothing circuit and double-ended converter

2000-05-16

2001-03-06

Han, Jessica (Department: 2838)

Electric power conversion systems

Current conversion

With means to introduce or eliminate frequency components

C363S017000, C363S126000

Reexamination Certificate

active

06198644

ABSTRACT:

TECHNICAL FIELD
This invention relates to a rectifying and smoothing circuit based on a current doubler rectification method, and a double-ended (bipolar) converter using the rectifying and smoothing circuit, such as a push-pull converter, a half-bridge converter, an asymmetric half-bridge converter, a full-bridge converter, and an active clamp converter.
BACKGROUND ART
Conventionally, as a power supply including a rectifying and smoothing circuit based on the current doubler rectification method of the above-mentioned kind, a power supply
81
shown in
FIG. 17
is known. This power supply
81
includes a switching transformer
2
, and a current doubler rectifying and smoothing circuit
82
. In this case, the current doubler rectifying and smoothing circuit
82
is comprised of a smoothing choke coil
14
connected between one end
2
b
1
of a secondary winding
2
b
of the transformer
2
and an output terminal
16
b
on a low-potential side, a smoothing choke coil
15
connected between the other end
2
b
2
of the secondary winding
2
b
and an output terminal
16
b
on a high-potential side and having the same inductance value as that of the choke coil
14
, a diode
11
as a rectifying element, connected between the one end
2
b
1
of the secondary winding
2
b
and an output terminal
16
a
, and a diode
12
as a rectifying element, connected between the other end
2
b
2
of the secondary winding
2
b
and the output terminal
16
a
. The current doubler rectifying and smoothing circuit
82
outputs a DC voltage V0 generated by rectifying and smoothing a bipolar voltage induced between the opposite ends of the secondary winding
2
b
to a load
4
.
In this power supply
81
, push-pull FET circuits, not shown, connected to one end
2
a
1
of a primary winding
2
a
of the transformer
2
and the other end
2
a
2
thereof, respectively, are driven at 180 degrees out of phase with respect to each other, whereby as shown in
FIG. 18
, a bipolar voltage VS having a voltage value±VS is induced between the opposite ends of the secondary winding
2
b
of the transformer
2
. In this case, in a period T1 during which one of the FET circuits is controlled to an ON state at a duty ratio D of 25%, a high voltage is induced on the side of the one end
2
b
1
of the secondary winding
2
b
during the ON time period TON of the FET, and this induced voltage causes a current I
31
shown in
FIG. 17
to flow through a current path of the one end
2
b
1
of the secondary winding
2
b
, the diode
11
, the load
4
, the choke coil
15
, and the other end
2
b
2
of the secondary winding
2
b
. In this state, as shown in
FIG. 18
, a voltage VL
15
having a voltage value (VS−V0=(1−D)/D−V0/f, where f represents a frequency of the bipolar voltage VS) and directed as shown in
FIG. 17
is generated between opposite ends of the choke coil
15
, whereby energy is accumulated in the choke coil
15
.
Further, during an OFF time period TOFF of the period T1, the energy accumulated in the choke coil
15
causes a current I
32
to flow in a direction shown in the same figure through a current path of one end of the choke coil
15
, the diode
12
, the load
4
, and the other end of the choke coil
15
. Consequently, the voltage VL
15
between the opposite ends of the choke coil
15
is caused to have a voltage (−V0), and at the same time, as shown in
FIG. 18
, a current IL
15
varying within a range of a current variation width ((VS−V0)•TON/Lo=(1−D)•V0/f, where Lo represents an inductance value of the choke coils
14
and
15
) flows through the choke coil
15
.
Further, in the period T2 (the same time period as the period T1) during which the other FET is controlled to an ON state at a duty ratio D of 25%, a high voltage is induced on the side of the other end
2
b
2
of the secondary winding
2
b
during the ON time period TON of the FET, and this induced voltage causes a current I
33
shown in
FIG. 17
to flow through a current path of the other end
2
b
2
of the secondary winding
2
b
, the diode
12
, the load
4
, the choke coil
14
, and the one end
2
b
1
of the secondary winding
2
b
. In this state, as shown in
FIG. 18
, between the opposite ends of the choke coil
14
is generated a voltage VL
14
having a voltage value (VS−V0) and directed as shown in
FIG. 17
, whereby energy is accumulated in the choke coil
14
.
Further, during an OFF time period TOFF of the period T2, the energy accumulated in the choke coil
14
causes a current I
34
to flow in a direction shown in
FIG. 17 through a
current path of one end of the choke coil
14
, the diode
11
, the load
4
, and the other end of the choke coil
14
. Consequently, the voltage VL
14
between the opposite ends of the choke coil
14
become equal to a voltage value (−V0), and as shown in
FIG. 18
, a current IL
14
varying within a range of a current variation width ((VS−V0)•TON/Lo=(1−D)•V0/f) flows through the choke coil
14
. In the above process of operation, each of average current values of the currents IL
15
and IL
14
becomes equal to one half of an output current I0, since a sum total of the current values of the currents becomes equal to the output current I0, shown in
FIGS. 17 and 18
, and at the same time the current values thereof are equal to each other. It should be noted that as shown in
FIGS. 17 and 18
, a ripple current IC flowing through the capacitor
13
varies within a range of a current variation width ((1−2D)•V0/f=(1−TON/(T−TON))•(VS−V0)•TON/Lo, where D represents a duty ratio, and f represents the reciprocal of the period T).
As described above, smoothing operations are carried out by the choke coils
14
and
15
during a time period of each of the periods T1 and T2, so that as shown in
FIG. 18
, an output current Io from which a ripple component is substantially eliminated is output to the load
4
.
DISCLOSURE OF THE INVENTION
The inventor studies the above prior art and found out the following problems:
Firstly, the conventional current doubler rectifying and smoothing circuit
82
uses the choke coils
14
and
15
constructed as separate component parts independent of each other. Therefore, the current doubler rectifying and smoothing circuit
82
has a large number of component parts and suffers from the problem of increased manufacturing costs caused by the mounting of component parts.
Secondly, a DC current having a predetermined current value constantly flows through the choke coils
14
and
15
, as shown in
FIG. 18
, respectively. In this case, as shown by the characteristics of the DC current with respect to the excitation inductance (LX) in
FIG. 16
, there is a predetermined relationship between the excitation inductance (LX) of smoothing coils (choke coils
14
and
15
in the above current doubler rectifying and smoothing circuit
82
) and a DC current allowed to pass through the smoothing coils. That is, to enhance the effect of the smoothing coils as smoothing filters, it is preferred that the smoothing coils have a large excitation inductance, whereas the value of a saturation DC current is reduced as the excitation inductance is increased. More specifically, when the effective volume of a smoothing choke coil as a magnetic material is small, if the excitation inductance is set to a small value (L
2
), as shown by a characteristic CH
1
, the smoothing choke coil can be used without magnetic saturation thereof until a current having a rather large current value (I
22
) flows therethrough, whereas if the excitation inductance is set to a large value (L
1
), there is a fear that the magnetic material undergoes magnetic saturation, since the limit value of a current below which the smoothing coil can be used without magnetic saturation thereof is lowered to a very small value (I
21
). Further, as shown by a characteristic CH
2
, when the effective volume of the coil as a magnetic material is made sufficiently large, if the excitation

Affiliated with

Also associated with

Rating

Rectifying/smoothing circuit and double-ended 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 Rectifying/smoothing circuit and double-ended converter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rectifying/smoothing circuit and double-ended converter will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2472877