Switching power supply device having series capacitance

Details Switching power supply device having series capacitance Switching power supply device having series capacitance

2001-09-21

2002-10-22

Riley, Shawn (Department: 2838)

Electric power conversion systems

Current conversion

Including d.c.-a.c.-d.c. converter

Reexamination Certificate

active

06469913

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to switching power supply devices for supplying DC stabilizing voltages. More particularly, the invention relates to switching power supply devices storing energy in the primary winding of a transformer and a capacitor during the ON-periods of a switching element and supplying the stored energy to a load from the secondary winding of the transformer during the OFF-periods of the switching element.
2. Description of the Related Art
In Japanese Patent Application No. 9-352696, there is provided a switching power supply device, in which a first switching circuit is connected to a second switching circuit on the primary winding side of a transformer T and switching control circuits alternately turn on and off switching elements included in the first and second switching circuits before and after periods during which both switching elements are turned off so that a self-excited oscillation is performed.
FIG. 1
is a block diagram illustrating the switching power supply device.
In this switching power supply device, an input power source E, an inductor L, and a first switching circuit S
1
are connected in series to a primary winding T
1
of a transformer T. Additionally, a series circuit composed of the primary winding T
1
and the inductor L is connected in parallel to a series circuit composed of a capacitor C and a second switching circuit S
2
. A first driving winding T
3
generates a voltage substantially proportional to a voltage of the primary winding T
1
. The voltage of the first driving winding T
3
is input to a control circuit
11
. Similarly, a second driving winding T
4
generates a voltage substantially proportional to a voltage of the primary winding T
1
. The voltage of the second driving winding T
4
is input to a control circuit
12
. The voltage of the control circuit
11
is input to a control terminal of a first switching element Q
1
of the first switching circuit S
1
. The voltage of the second control circuit
12
is input to a control terminal of a second switching element Q
2
of the second switching element S
2
. The first switching circuit S
1
is formed by a parallel connection circuit composed of the first switching element Q
1
, a first diode D
1
, and a first capacitor C
1
. The second switching circuit S
2
is formed by a parallel connection circuit composed of the second switching element Q
2
, a second diode D
2
, and a second capacitor C
2
.
A rectifying element Ds is connected in series to the secondary winding T
2
of the transformer T. A rectifying and smoothing circuit is composed of the rectifying element Ds and a capacitor Co connected to an output of the rectifying element Ds. The rectifying element Ds is connected in parallel to a capacitor (capacitive impedance) Cs. A detection circuit
14
detecting the voltage of a load is connected between an output of the rectifying and smoothing circuit and the load. An output feedback of the detection circuit
14
is sent to the first control circuit
11
.
In addition. U.S. Pat. No. 3,596,165 provides a switching power supply device, in which two switching circuits are connected to each other on the primary winding side of a transformer to perform separately-excited oscillation and a fullwave rectifier is connected to the secondary winding.
Furthermore, in Japanese Unexamined Patent Application Publication No. 5-328719 and Japanese Unexamined Patent Application Publication No. 11-136940, there are provided switching power supply devices. In each of the devices, two switching circuits are connected to each other on the primary winding of a transformer and a secondary-side winding is formed by a circuit structure as shown in FIG.
1
. In this case, an inductor and a capacitor are connected in series to the primary winding. A second switching element is connected in parallel to the series circuit.
In each of the switching power supply devices above, however, there are problems as follows.
(1) U.S. Pat. No. 3,596,165
The switching power supply device is a circuit referred to as a resonant-type half-bridge circuit (ON-ON type). In this type of circuit, when each switching element is turned on. energy is transmitted from the primary winding to the secondary winding. The ON-time of each of the switching elements is substantially fixed and the switching frequency is changed to change the impedance of an LC resonant circuit connected in series to the primary winding so as to control an output power. In other words, when the LC resonant frequency and the switching frequency are close to each other, the impedance of the LC resonant circuit becomes smaller. whereby a large current flows through the transformer. so that a large output power can be obtained. In contrast, when the LC resonant frequency is far from the switching frequency, a small output power can be obtained. In such an arrangement, according to the output power, the switching frequency changes significantly. When the frequency greatly changes, the dimensions of an output smoothing circuit and a filter circuit also increase. As a result, there are problems such as interference with electronic components and increase in loss in the control circuits.
Additionally, since the switching power supply device is a separately excited oscillation type of device, the number of components increases, which hinders miniaturization of the device and cost reduction. Furthermore, in order to perform full-wave rectification, at least two diodes are required on the secondary side of the transformer.
(2) Japanese Unexamined Patent Application Publication No. 5-328719 and Japanese Unexamined Patent Application Publication No. 11-136940
Each of the switching power supply devices provided in the publications is an ON-OFF type switching power supply device in which energy is stored in the primary winding during the ON-times of switching elements and the stored energy is discharged from the secondary winding during the OFF-times of the switching elements. However, each of the devices is not a self-excited oscillation type but a separately excited oscillation type or a synchronous oscillation type. Thus, since the device requires an oscillator, a drive circuit, and the like, the number of components increases, thereby hindering miniaturization of the device and cost reduction. In Japanese Unexamined Patent Application Publication No. 5-328719, since a synchronous oscillation circuit is used, an oscillator is not required. Nevertheless, the power supply device needs an IC including a MOS-FET having high voltage breakdown properties to drive a high-side switching element. a pulse transformer for isolation and drive, and so on. As a result, in even the switching power supply device, the size of the switching control circuit and production cost increase.
(3) Japanese Patent Application No. 9-352696
The switching power supply device provided in this publication is a self-excited oscillation type, which is an ON-OFF type switching power supply device storing energy in the primary winding during the ON-time of a first switching circuit and discharging the stored energy from the secondary winding during the OFF-period of the first switching circuit. As shown in
FIG. 1
, since a voltage equivalent to the sum of an input voltage Vin and a capacitor voltage Vc is applied to a switching element, the switching element needs to be an element having high voltage breakdown properties. In addition, since the power supply device has a structure in which the input voltage Vin is directly applied to the primary winding T
1
of a transformer T, the voltage applied to the primary winding T
1
becomes higher, which hinders miniaturization of the device.
Furthermore, only excitation energy stored in the primary winding of the transformer is output to the secondary side of the transformer. The energy of the capacitor C is not output to the secondary side. As a result, a peak current value of the primary winding becomes larger, thereby increasing conduction loss.
SUMMARY OF THE INVENTION
Accordingly, it is an o

Affiliated with

Also associated with

Rating

Switching power supply device having series capacitance 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 device having series capacitance, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Switching power supply device having series capacitance will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2980045