Resonant converter circuit

Details Resonant converter circuit Resonant converter circuit

2000-11-22

2003-09-16

Sherry, Michael (Department: 2838)

Electric power conversion systems

Current conversion

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

C363S127000, C363S089000

Reexamination Certificate

active

06621718

ABSTRACT:

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.


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patent: 5140510 (1992-08-01), Myers
patent: 5140513 (1992-08-01), Yokoyama
patent: 5386359 (1995-01-01), Nochi
patent: 5521807 (1996-05-01), Chen et al.
patent: 5640082 (1997-06-01), Lusher et al.
patent: 5684678 (1997-11-01), Barrett
patent: 5702431 (1997-12-01), Wang et al.
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patent: 6101102 (2000-08-01), Brand et al.
patent: 6151222 (2000-11-01), Barrett
patent: 6301128 (2001-10-01), Jang et al.
patent: 0788217 (1997-08-01), None
patent: 5344722 (1993-12-01), None

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