Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2001-09-06
2003-03-04
Berhane, Adolf Deneke (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S097000
Reexamination Certificate
active
06529392
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ringing choke converter type switching power supply unit.
2. Description of the Related Art
Up to now, a ringing choke converter (hereinafter, referred to as RCC) type switching power supply unit has been known for use as a switching power supply unit. This RCC type switching power supply unit is to provide a stabilized DC power supply using a commercially available AC power supply, and, as the construction is relatively simple and the power supply unit is small-sized, light-weight, and highly efficient, it is widely used in various devices such as electronic computers, communication devices, office automation equipment, etc. Furthermore, this type of power supply unit is also utilized as an auxiliary unit and a pre-regulator in small capacity series regulators.
FIG. 8
is a circuit diagram of a conventional RCC type switching power supply unit. As shown in the drawing, the switching power supply unit
10
is composed of an input circuit
2
, a DC-DC converter circuit
3
, a voltage detector circuit
4
, and a control circuit
5
.
The input circuit
2
is composed of a fuse F, a filter circuit LF, and a rectifying diode bridge DB, and an alternating-current power supply AC is connected to the input terminals. Furthermore, one input terminal of the input circuit
2
is connected to one end of the input-side of the filter circuit LF through the fuse F and the other input terminal of the input circuit
2
is directly connected to the other end of the input side of the filter circuit LF. Furthermore, the terminals on the output side of the filter circuit LF are connected to respective input terminals of the diode bridge DB. The output terminals a and b of the diode bridge DB are connected to the input terminals a and b of the DC—DC converter circuit
3
.
The DC—DC converter circuit
3
is composed of capacitors C
1
and C
4
, a transformer T, a main switching element such as MOS field-effect transistor (FET) Q
1
as resistors R
1
and R
10
, and a diode D
1
. Furthermore, the transformer T contains a primary winding N
1
, a secondary winding N
2
which is opposite in polarity to the primary winding N
1
, and a feedback winding Nb which is the same in polarity as the primary winding N
1
. The smoothing capacitor C
1
is provided between the input terminals a and b of the DC—DC converter circuit
3
, and also a series circuit of the primary winding N
1
and the FET Q
1
is provided so as to be parallel to the capacitor C
1
. Thus, the starting point of the primary winding N
1
of the transformer T is connected to the input terminal a of the DC—DC converter circuit
3
, the drain of the FET Q
1
is connected to the end of the primary winding N
1
, and the source of the FET Q
1
is connected to the input terminal b of the DC—DC converter circuit
3
. Furthermore, one end of the starter resister R
1
is connected to the starting point of the primary winding N
1
, and the other end of the resistor R
1
is connected to the gate of the FET Q
1
. The resistor R
10
is connected between the gate and the source of the FET Q
1
. Moreover, the anode of the rectifying diode D
1
is connected to the end of the secondary winding N
2
of the transformer T, and the smoothing capacitor C
4
is connected between the cathode of the diode D
1
and the starting point of the secondary winding N
2
. The diode D
1
and capacitor C
4
constitute a rectifying and smoothing circuit.
The voltage detector circuit
4
is provided on the output side of the DC—DC converter circuit
3
, and is composed of resistors R
5
, R
6
, and R
7
, a light-emitting diode PD as a light-emitting device of a photo coupler PC, and a shunt regulator Sr. The output terminals of the voltage detector circuit
4
are provided so as to be parallel to the capacitor C
4
of the DC—DC converter circuit
3
. Furthermore, each of a series circuit of the resistor R
5
, the light-emitting diode PD, and the shunt regulator Sr, and a series circuit of the resistors R
6
and R
7
is provided so as to be parallel to the capacitor C
4
. Moreover, the cathode of the light-emitting diode PD and the cathode of the shunt regulator Sr are connected. Furthermore, the reference terminal of the shunt regulator Sr is connected to the connection point between the resistors R
6
and R
7
.
The control circuit
5
is composed of resistors R
2
, R
3
, R
4
, and R
13
, capacitors C
2
and C
3
, a diode D
2
, a phototransistor PT as a light receiving element of a photo coupler PC, and an NPN transistor Q
2
. The capacitor C
3
and the resistor R
13
are connected in series between the gate of the FET Q
1
of the DC—DC converter circuit
3
and the starting point of the feedback winding Nb. Furthermore, the collector and the emitter of the transistor Q
2
are connected to the gate and the source of the FET Q
1
, respectively. Moreover, a series circuit of the resistor R
2
and the resistor R
3
is connected between the starting point and the end of the feedback winding Nb. In addition, a series circuit of the resistor R
4
, the diode D
2
, and the phototransistor PT in the photo coupler PC is connected so as to be parallel to the resistor R
2
. Moreover, the cathode of the diode D
2
is connected to the collector of the phototransistor PT in the photo coupler PC. Furthermore, the capacitor C
2
is connected between the base and the emitter of the transistor Q
2
, and the above resistor R
3
is connected so as to be parallel to the capacitor C
2
.
Next, the operation of the switching power supply unit
10
constructed as in the above is described. First, at the start where the power supply is turned on, a voltage is applied to the gate of the FET Q
1
through the starter resistor R
1
and the FET Q
1
is turned on. In this way, the voltage of the power supply is applied to the primary winding N
1
of the transformer T and a voltage having the same polarity as that of the primary winding N
1
is generated in the feedback winding Nb. This voltage signal as a positive feedback signal is provided to the gate of the FET Q
1
through the resistor R
13
and the capacitor C
3
, and the FET Q
1
is quickly turned on. At this time, an excitation energy is stored in the primary winding N
1
.
A charging current flows into the capacitor C
2
through the resistor R
2
because of the electromotive force in the feedback winding Nb. When the charging voltage of the capacitor C
2
exceeds the forward voltage drop between the base and the emitter of the controlling transistor Q
2
, the transistor Q
2
is turned on. In this way, the voltage between the gate and the source of the FET Q
1
becomes substantially zero thereby to turn off the FET Q
1
.
Thus, the excitation energy stored in the primary winding N
1
of the transformer T during the ON-state period of the FET Q
1
is discharged as electric energy through the secondary winding N
2
, rectified by the diode D
1
, smoothed by the capacitor C
4
, and supplied to the load (not shown in the drawing) which is connected to the output terminals of the voltage detector circuit
4
.
When the electric charge in the charged capacitor C
2
is discharged through a discharge circuit of the resistor R
3
, etc., and the charged voltage becomes equal to or less than the forward voltage drop between the base and the emitter of the transistor Q
2
, the transistor Q
2
is turned off. Furthermore, when the excitation energy stored in the primary winding N
1
of the transformer T is discharged through the secondary winding N
2
and the current flowing through the diode D
1
becomes zero, a kickback voltage is generated in the feedback winding Nb in which the starting point of the winding is positive polarity and the FET Q
1
is turned on by the kickback voltage once again. When the FET Q
1
is turned on, a voltage is provided to the primary winding N
1
of the transformer T again, and an excitation energy is stored in the primary winding N
1
.
Thus, the above-described oscillation is repeated in the switching power supply unit
10
.
Next, the feedback control by t
Nakahira Koji
Nishida Akio
Tani Ryota
Berhane Adolf Deneke
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
LandOfFree
Switching power supply unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Switching power supply unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Switching power supply unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3052101