Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2000-07-12
2001-05-22
Nguyen, Matthew (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S021070, C363S021150
Reexamination Certificate
active
06236578
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a power supply, and more particularly, to a power supply which can convert an oscillating voltage into a variable steady state voltage.
2. Description of the Prior Art
Please refer to FIG.
1
.
FIG. 1
is a perspective view of a prior art power supply
10
. The power supply
10
is used for converting an oscillating voltage
12
into a steady state voltage which is then outputted to a display device
16
through an output port
14
. The power supply
10
comprises a voltage converting circuit
18
, a transformer
22
, a pulse generator
26
, a light coupling device
36
, a rectifying circuit
30
and a feedback circuit
34
.
The voltage converting circuit
18
comprises a bridge circuit
38
and a filter
40
for rectifying the oscillating voltage
12
into a first steady state voltage. The transformer
22
has an input end
20
, an output end
24
and a control end
28
. The input end
20
is electrically connected to an output end
42
of the voltage converting circuit
18
. The transformer
22
is used for transforming the first steady state voltage at the input end
20
into a second oscillating voltage at the output end
24
. The control end
28
is used for controlling on and off of the transformer
22
. The pulse generator
26
has an output end
44
and a control end
46
. The output end
44
is electrically connected to the control end
28
of the transformer
22
. The pulse generator
26
is used for generating a pulse signal at the output end
44
so as to control the on and off of the transformer
22
. The control end
46
is used for controlling a duty cycle of the pulse signal. The rectifying circuit
30
has an input end
32
electrically connected to the output end
24
of the transformer
22
for rectifying the second oscillating voltage so as to generate the steady state voltage at the output port
14
of the power supply
10
.
The feedback circuit
34
has an input end
50
, a control end
56
and an output end
52
. The input end
50
is electrically connected to the output end
48
of the rectifying circuit
30
. The light coupling device
36
is electrically connected between the output end
52
of the feedback circuit
34
and the control end
46
of the pulse generator
26
for isolating the current between the output end
52
of the feedback circuit
34
and the control end
46
of the pulse generator
26
. The feedback circuit
34
comprises a comparator
54
for comparing the voltage at the control end
56
with a predetermined voltage so as to generate a control signal, and a variable resistor
58
for fixing errors caused by other resistive components.
When the voltage at the control end
56
is higher than the predetermined voltage, the impedance of the comparator
54
will drop thus grounding the output end
52
, turning on the light coupling device
36
, and generating an offset voltage at the control end
46
of the pulse generator
26
. When detecting the offset voltage, the pulse generator
26
will gradually reduce the duty cycle of the pulse signal generated at the output end
44
. When the voltage at the control end
56
is lower than the predetermined voltage, the impedance of the comparator
54
will increase thus turning off the light coupling device
36
and grounding the control end
46
of the pulse generator
26
. And the pulse generator
26
will gradually increase the duty cycle of the pulse signal generated at its output end
44
.
The feedback circuit
34
can control the pulse generator
26
to sustain the steady state voltage at the output port
14
at only one fixed voltage, and the power supply
10
has no component to change the steady state voltage. Therefore, the power supply
10
can not generate different steady state voltages for different display devices.
SUMMARY OF THE INVENTION
It is therefore a primary objective of the present invention to provide a power supply to solve the aforementioned problem.
According to the claimed invention, the power supply can convert an inputted oscillating voltage into an outputted steady state voltage. The power supply comprises a feedback circuit having a first input end electrically connected to the outputted steady state voltage and a second input end electrically connected to a variable power source. By controlling the variable power source, the outputted steady state voltage can be varied.
It is an advantage of the present invention that the outputted steady state voltage can be controlled by the variable power source so that the power supply can generate different steady state voltages for different display devices.
These and other objects and the advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment, as illustrated by the included figures and drawings.
REFERENCES:
patent: 4316242 (1982-02-01), Colangelo et al
patent: 5629841 (1997-05-01), Attwood
patent: 5675485 (1997-10-01), Seong
patent: 5914865 (1999-06-01), Barbehenn et al.
Acer Peripherals Inc.
Hsu Winston
Nguyen Matthew
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