Resonant converter circuit
专利汇可以提供Resonant converter circuit专利检索，专利查询，专利分析的服务。并且A power converter circuit is disclosed. The power converter circuit comprises an oscillator for receiving an input wherein the oscillator operates with a fixed frequency and a resonant circuit coupled to the oscillator, wherein the resonant circuit is adjusted to minimize switching losses. Through the use the power converter circuit in accordance with the present invention, high switching losses are avoided thereby resulting in an increase in the overall efficiency of the power converter circuit.，下面是Resonant converter circuit专利的具体信息内容。
What is claimed is:1. A resonant converter circuit comprising:an oscillator for receiving an input wherein the oscillator operates with a fixed frequency;a resonant circuit coupled to the oscillator, the resonant circuit comprising a transformer, at least two capacitors in series coupled to a secondary winding of the transformer, and a switch coupled to one of the at least two capacitors; anda pulse width modulator coupled to the resonant circuit, wherein the pulse width modulator is utilized to vary a capacitance of the resonant circuit.2. The resonant converter circuit of claim 1 wherein the circuit further comprises:an error amplifier coupled to the pulse width modulator for receiving an output.3. The resonant converter circuit of claim 1 wherein the pulse width modulator turns the switch on and off at a variable rate.4. The resonant converter circuit of claim 3 wherein the oscillator comprises a square wave oscillator.5. The circuit of claim 4 wherein the square wave oscillator is coupled to two switches wherein the switches operate in a zero voltage switch mode.6. A resonant converter circuit comprising:a square wave oscillator for receiving an input wherein the oscillator operates with a fixed frequency;a resonant circuit coupled to the square wave oscillator, the resonant circuit comprising:a transformer;at least two capacitors in series coupled to a secondary winding of the transformer; anda switch coupled to one of the at least two capacitors; anda pulse width modulator coupled to the switch wherein the pulse width modulator is utilized to vary a capacitance of the resonant circuit.7. The resonant converter circuit of claim 6 further comprising an error amplifier coupled to the pulse width modulator for receiving an output.8. The resonant converter circuit of claim 7 wherein the square wave oscillator is coupled to two switches wherein the switches operate in a zero voltage switch mode.9. A power converter circuit comprising:a square wave oscillator for receiving an input wherein the oscillator operates with a fixed frequency;two switches coupled to the square wave oscillator wherein the two switches operate in a zero voltage switch mode;a resonant circuit coupled to the square wave oscillator, the resonant circuit comprising:an inductor;a transformer coupled to the inductor;at least two capacitors in series coupled to a secondary winding of the transformer; anda switch coupled to one of the at least two capacitors;a pulse width modulator coupled to the resonant circuit via the switch wherein the pulse width modulator is utilized to vary a capacitance of the resonant circuit; andan error amplifier coupled to the pulse width modulator for receiving an output.
FIELD OF THE INVENTION
The present invention relates generally to power supply systems and particularly to a power converter circuit.
BACKGROUND OF THE INVENTION
A typical switching-type power converter circuit operates by storing and releasing energy in various discrete capacitive and inductive components during each cycle of operation, where the time interval for each cycle is determined by the switching frequency. An increase in switching frequency reduces the storage time interval and the level of energy stored in reactive components during any one particular cycle of operation. In principle this increase in frequency permits reduction of both the physical and electrical sizes of magnetic and capacitive storage elements for any particular power capacity.
Please refer now to FIG.
1
(
a
). FIG.
1
(
a
) is a high level illustration of a conventional switching-type power converter circuit
10
. The circuit
10
includes an input
11
, a variable frequency voltage control oscillator
14
, a fixed frequency resonant circuit
15
, filter components
25
, an error amplifier
36
, and an output
38
. The voltage control oscillator
14
is coupled to the resonant circuit
15
and the error amplifier
36
wherein the error amplifier
36
is coupled to the output
38
. The resonant circuit
15
is coupled to the filter components
25
wherein the filter components
25
are coupled to the output
38
.
For a more detailed description of the conventional switching-type power converter circuit
10
, please refer now to the FIG.
1
(
b
). Shown in the figure are the input
11
, first, second, third and fourth capacitors
12
,
18
,
28
,
34
, the voltage control oscillator
14
, two switches
16
,
20
, first and second inductors
22
,
32
, a transformer
24
, two diodes
26
,
30
, an error amplifier
36
, and an output
38
.
The input
11
is coupled to the first capacitor
12
and the first switch
16
wherein the first switch
16
is coupled to the voltage control oscillator
14
and the second switch
20
. The voltage control oscillator
14
is also coupled to the second switch
20
and the first capacitor
12
is coupled to the transformer
24
. The first and second switches
16
,
20
are coupled to the second capacitor
18
wherein the second capacitor
18
is coupled to the first inductor
22
. The first inductor
22
is coupled to the transformer
24
wherein the transformer
24
is coupled to the third capacitor
28
. The third capacitor
28
is coupled to the first and second diodes
26
,
30
wherein the first and second diodes
26
,
30
are coupled to the second inductor
32
. The second inductor
32
is coupled to the fourth capacitor
34
wherein the fourth capacitor
34
is coupled to the output
38
. The output
38
is coupled to the error amplifier
36
wherein the error amplifier
36
is coupled to the voltage control oscillator
14
.
The resonant circuit
15
comprises the first inductor
22
, transformer
24
and the third capacitor
28
. The filter components
25
comprise the two diodes
26
,
30
, the second inductor
32
and the fourth capacitor
34
. The second capacitor
18
develops almost half of the DC input voltage and also prevents the transformer
24
from saturating. The first inductor
22
is a leakage inductor for the transformer
24
and the two diodes
26
,
30
are used for rectifying a sine wave voltage that is developed across the third capacitor
28
.
During operation, the circuit
10
operates over a wide range of load conditions wherein the output
38
of the power converter circuit
10
is a regulated output. The output
38
is regulated by allowing the error amplifier
36
to sense the output DC voltage. Because the output DC voltage has a tendency to change from its set voltage, the error amplifier
36
subsequently develops a voltage that will vary the frequency of voltage control oscillator
14
. A square wave of different frequency applied across the fixed frequency resonant circuit
15
will increase or decrease the voltage developed across the fourth capacitor
34
thereby increase or decreasing the voltage at the output
38
.
Because the switches
16
,
20
each experience full voltage when being turned on, the circuit
10
can not operate in a zero voltage switching (ZVS) mode. Consequently, since the circuit can not operate in a ZVS mode, as the frequency increases, the switching losses incurred by the two switches
16
,
20
increases. These losses become significant at frequencies of 5 megahertz or higher.
Accordingly, what is needed is an improved converter circuit. The circuit should be simple, cost effective, and easily adaptable to existing technology. The present invention addresses such a need.
SUMMARY OF THE INVENTION
A power converter circuit is disclosed. The power converter circuit comprises an oscillator for receiving an input wherein the oscillator operates with a fixed frequency and a resonant circuit coupled to the oscillator, wherein the resonant circuit is adjusted to minimize switching losses.
Through the use the power converter circuit in accordance with the present invention, high switching losses are avoided thereby resulting in an increase in the overall efficiency of the power converter circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG.
1
(
a
) is a high level illustration of a conventional switching-type power converter circuit.
FIG.
1
(
b
) is a more detailed description of the conventional switching-type power converter circuit of FIG.
1
(
a
).
FIG.
2
(
a
) is a high level illustration of a converter circuit in accordance with the present invention.
FIG.
2
(
b
) is a more detailed description of the converter circuit in accordance with the present invention.
DETAILED DESCRIPTION
The present invention relates to a power converter circuit. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein.
The present invention is disclosed in the context of a preferred embodiment. The present invention provides for a power converter circuit for a computer system wherein the power converter circuit includes a variable frequency resonant circuit. In accordance with the present invention, the capacitance of the resonant circuit is varied in order to provide a regulated output without changing the frequency of the voltage oscillator. By keeping the frequency of the voltage oscillator constant, high switching losses are avoided thereby resulting in an increase in the overall efficiency of the power converter circuit.
Please refer now to FIG.
2
(
a
). FIG.
2
(
a
) is a high level illustration of a power converter circuit
50
in accordance with the present invention. The circuit
50
includes an input
51
, a fixed frequency oscillator
54
, a variable frequency resonant circuit
65
, filter components
75
, an output
80
, an error amplifier
82
and an pulse width modulator
84
. The fixed frequency oscillator
54
is coupled to the variable frequency resonant circuit
65
and the variable frequency resonant circuit
65
is coupled to the filter components
75
and the pulse width modulator
84
. The pulse width modulator
84
is coupled to the error amplifier
82
wherein the error amplifier
82
is coupled to the output
80
.
For a more detailed description of the power converter circuit
50
in accordance with the present invention, please refer now to the FIG.
2
(
b
). Shown in the figure are the input
51
, a first capacitor
52
, the fixed frequency oscillator
54
, first and second switches
56
,
60
, a second capacitor
58
, the resonant circuit
65
, and the filter components
75
. The resonant circuit
65
comprises a first inductor
62
, a transformer
64
, third and fourth capacitors
66
,
68
and a third switch
70
. The filter components
75
comprises the two diodes
72
,
74
, a second inductor
76
, and a fifth capacitor
78
.
The input
51
is coupled to the first capacitor
52
and the first switch
56
wherein the first switch
56
is coupled to the fixed frequency oscillator
54
and the second switch
60
. The fixed frequency oscillator
54
is also coupled to the second switch
60
. The first and second switches
56
,
60
are coupled to the second capacitor
58
wherein the second capacitor
58
is coupled to the first inductor
62
. The first inductor
62
is coupled to the transformer
64
wherein the transformer
64
is coupled to the third capacitor
66
and the second diode
74
. The third capacitor
66
is coupled to the fourth capacitor
68
and the third switch
70
. The first and second diodes
72
,
74
are coupled to the second inductor
76
wherein the second inductor
76
is coupled to the fifth capacitor
78
and the output
80
. The output
80
is coupled to the error amplifier
82
wherein the error amplifier
82
is coupled to the pulse width modulator
84
. The pulse width modulator
84
is coupled to the third switch
70
.
By utilizing the circuit
50
in accordance with the present invention, the frequency of the oscillator
54
is kept constant while the capacitance of the resonant circuit is varied. Preferably, the fixed frequency oscillator
54
comprises a square wave oscillator. (The square wave produced by the square wave oscillator
54
becomes a sine wave when the square wave is applied to the resonant circuit.) The capacitance of the resonant circuit is varied by utilizing the pulse width modulator
84
to turn the third switch
70
on and off based on a duty ratio. What is meant by duty ratio is the amount of time that the switch
70
is “on” divided by the total cyclical period. Therefore, if the switch is on for 5 microseconds and off for 5 microseconds, the total period is 10 microseconds. Hence, a duty ratio of 5 divided by 10 or 1/2.
The duty ratio of the pulse width modulator
84
is determined by the output of the error amplifier
82
. Consequently, the effective capacitance of the resonant circuit is:
C
res
=
C
3
×
D
(
C
4
)
C
3
+
D
(
C
4
)
where C
res
is the total capacitance of the resonant circuit, C
3
is the capacitance of the third capacitor
66
, D is the duty ratio of the third switch
70
and C
4
is the capacitance of the fourth capacitor
68
. In addition, the switches
56
,
60
operate at a 50% duty cycle. That is to say that when switch
56
is on, switch
60
is off and vice versa. Because the frequency of the oscillator
54
is fixed, each of the switches
56
,
60
are able to be turned on at time when there is no voltage across it. Therefore, the circuit
50
in accordance with the present invention operates in a ZVS mode which results in a substantial reduction in switching losses due to hard turn ons.
Although the preferred embodiment of the present invention is described in the context of having a single output, one of ordinary skill in the art will readily recognize that the present invention can be utilized with multiple outputs while remaining within the spirit and scope of the present invention. This can be achieved, for example by coupling multiple resonant circuits to the fixed frequency oscillator.
In accordance with the present invention, by keeping constant the frequency of the oscillator and varying the capacitance of the resonant circuit based on the duty ratio of the pulse width modulator, the circuit is able to operate in a ZVS mode. Because the circuit operates in a ZVS mode, the high switching losses incurred through the use of conventional converter circuits are avoided. This results in an increase in circuit efficiency.
Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present invention. For example, although the preferred embodiment of the present invention describes varying the capacitance of the resonant circuit, the inductance of the resonant circuit could be varied instead. Accordingly, many modifications may be made by one or ordinary skill in the art without departing from the spirit and scope of the appended claims.
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