Electric power conversion systems – Current conversion – With condition responsive means to control the output...
Reexamination Certificate
2001-09-13
2003-02-18
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Current conversion
With condition responsive means to control the output...
C323S282000
Reexamination Certificate
active
06522560
ABSTRACT:
FIELD OF THE INVENTION
The present invention is generally in connection with a power supply apparatus, and more particularly, the present invention is in connection with a power supply apparatus of simplified circuit arrangement and miniaturized magnetic element dimension.
DESCRIPTION OF THE PRIOR ART
As depicted in
FIG. 1
, a switching regulator which functions as a basic power supply apparatus typically comprises a power stage circuit and a voltage feedback circuit. The power stage circuit principally includes a switching circuit comprising a main transformer T
1
, a primary power train circuit
111
, a control circuit
114
and two voltage switches Q
1
and Q
2
. The primary power train circuit
111
is employed to receive an input voltage V
in
and provides an output voltage to the primary side L
11
of the main transformer T
1
in accordance with an oscillating pulse signal
112
. The oscillating pulse signal
112
is provided by a primary control circuit
113
which is coupled to the primary power train circuit
111
and may preferably comprise a pulse width modulation integrated circuit (PWM IC), such as
3843
or
3844
series integrated circuit chip. The control circuit
114
is used to output switch control signals to respectively control the switch operation of the on/off states of the two voltage switches Q
1
and Q
2
, whereby rectifying the voltage at the secondary side L
12
of the main transformer T
1
by means of the switch operation of the two voltage switches Q
1
and Q
2
. The power stage circuit further comprises an output low-pass filter
115
, which includes an inductor
1151
and a capacitor
1152
for providing a DC (direct current) output voltage V
0
to a load
110
. The control circuit
114
which generates switch control signals to turn the transistor switches Q
1
and Q
2
on and off generally is driven by an oscillating pulse signal
119
to initialize its control function, in order that the voltage at the secondary side L
12
of the main transformer T
1
may be rectified in synchronization with the phase of the oscillating pulse signal
119
.
Furthermore, for the purpose of stabilizing the output voltage V
0
of the switching regulator, a voltage feedback circuit is required to be coupled between the output voltage V
0
of the switching regulator and the input voltage V
in
. The voltage feedback circuit comprises a secondary feedback control circuits
117
which detects the DC output voltage V
0
and generates a voltage feedback control signal in response to the output voltage V
0
. The voltage feedback circuit further comprises a photo coupler
116
which is coupled in series between the secondary feedback control circuit
117
and the primary control circuit
113
for coupling the voltage feedback control signal to the primary control circuit
113
to actuate the voltage feedback control function of the primary control circuit
113
. In this way, the DC output voltage V
0
can be insulated from the primary side L
11
and the secondary side L
12
of the main transformer T
1
by means of the photo coupler
116
.
As explained above, in order to assure that the control circuit
114
which controls the on/off states of the voltage switches Q
1
and Q
2
can rectify the voltage at the secondary side L
12
of the main transformer T
1
to a desired voltage, an oscillating pulse signal
119
is needed to be applied to the control circuit
114
so that the control circuit
114
can rectify the voltage at the secondary side L
12
of the main transformer T
1
in synchronization with the phase of the oscillating pulse signal
119
. The oscillating pulse signal
119
is typically transmitted from a driver transformer T
2
coupled with the primary control circuit
113
. The primary side of the driver transformer T
2
receives an oscillating pulse signal from the primary control circuit
113
, and at the same time an equivalent oscillating pulse signal
119
is induced on the secondary side of the driver transformer T
2
. The induced oscillating signal
119
acts as a driving signal to drive the control circuit
114
to rectify the voltage at the secondary side L
12
of the main transformer T
1
by means of the switch operations of the voltage switches Q
1
and Q
2
.
Still referring to
FIG. 1
, in order to startup the control function of the secondary feedback control circuit
117
, an external auxiliary power source
118
is required to be connected to the secondary feedback control circuit
118
to provide sufficient power to initialize the secondary feedback control circuit
117
.
FIG. 2
, FIG.
3
and
FIG. 4
illustrate several modified circuit configurations of the switching regulator of FIG.
1
. In
FIG. 4
, the photo coupler which is employed to isolate the DC output voltage V
0
of the switching regulator from the primary side L
11
and the secondary side L
12
of the main transformer T
1
is removed from the voltage feedback circuit, and a magnetic element T
3
is coupled between the primary control circuit
113
and the secondary feedback control circuit
117
for coupling the voltage feedback control signal from the secondary feedback control circuit
117
to the primary control circuit
113
. A rectifier circuit
20
is further coupled in series between the magnetic element T
3
and the secondary feedback control circuit
117
for rectifying the voltage induced at the secondary side of the magnetic element T
3
into a DC voltage, and the rectified DC voltage is taken as the auxiliary power source for operating the secondary feedback control circuit
117
.
Nonetheless, the performance of the photo coupler
116
is susceptible to the ambient temperature and incident light beam, and thus the mean time before value (MTBF) of the conventional power supply apparatus will get worsened gradually. In addition, the number of the magnetic elements in the power supply apparatus is a decisive factor for the size of the power supply apparatus. The more magnetic elements presented in a power supply apparatus, the larger size the power supply apparatus will occupy. Moreover, the large number of the magnetic elements in a power supply apparatus implicitly indicates that the circuit arrangement of the power supply apparatus will be much complicated, which might become a handicap of designing the power supply apparatus to fit the requirements of compactness and low-cost.
There is a tendency to look for a way to integrate the functionalities of driving the control circuit at the secondary side of the main transformer to carry out synchronous rectification, coupling the voltage feedback control signal to the control circuit at the primary side of the transformer, and providing the auxiliary power required to operate the feedback control circuit of the voltage feedback circuit, into an unitary magnetic element for use in a power supply apparatus.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a power supply apparatus for regulating an input voltage to provide an output voltage to a load is provided and comprises a power stage circuit including a switching circuit for receiving and rectifying an input voltage and an output filter for providing an output voltage to a load, and a voltage feedback circuit coupled between the output voltage and the input voltage, wherein the voltage feedback circuit includes a feedback control circuit for detecting the output voltage and outputting a voltage feedback control signal in response to the output voltage, a control circuit for outputting a first oscillating signal to the switching circuit, a magnetic element coupled in series between the feedback control circuit and the control circuit for receiving a second oscillating signal from the control circuit and coupling the second oscillating signal to the switching circuit and coupling the voltage feedback control signal to the control circuit, and a rectifier circuit coupled in series between the feedback control circuit and the magnetic element for rectifying the second oscillating signal into an auxiliary voltage for operating the feedback co
Fan Heng-Chia
Hsiao Ko-Yu
Lin Hsin-Liang
Lin Wei-Ming
Delta Electronics , Inc.
Eldredge John W.
Patel Rajnikant B.
Stradling Yocca Carlson & Rauth
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