Two stage power converter with interleaved buck regulators

Details Two stage power converter with interleaved buck regulators Two stage power converter with interleaved buck regulators

2000-05-18

2001-04-03

Wong, Peter S. (Department: 2838)

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

C323S284000

Reexamination Certificate

active

06211657

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to power supplies. More particularly, the present invention relates to high voltage low ripple power converters.
2. Background Art
In certain applications requiring a high voltage power source, it is desirable that the power source is substantially free of ripple effects. One known method of generating regulated high DC voltage at high power level involves rectifying an AC power source (e.g., 208 VAC, 60 Hz) and then converting the rectified DC voltage into high voltage using a high frequency switching converter. In such a scheme, the low frequency ripple components, mainly the line harmonics, are attenuated by a voltage feedback loop, whereas the high frequency components, produced by the switching converter, are greatly reduced by an LC output filter. Increasing the switching frequency makes the filtering easier—the feedback loop gain can be increased which improves input ripple rejection, and the low pass filter (removing switching noise from the output) becomes more effective. On the other hand, the higher switching frequency reduces the efficiency of the power converter. The objective is to find a topology that would allow the power converter to operate at a high frequency and with a good efficiency and to produce low noise, high stability, and high voltage output.
FIG. 1
is a schematic diagram of a two-stage power converter in accordance with the prior art. The converter
10
includes a buck regulator stage
12
and a bridge stage
14
. A transformer
17
is also shown. The converter operates as follows. A three-phase power source (e.g., 208 volts at 60 hertz) is applied to rectifier
16
. Unregulated rectified DC power is applied to the buck regulator stage
12
, which includes a single buck regulator. The buck regulator comprises a switch
20
, an inductor
30
, and a diode
25
. The buck regulator
12
produces DC pulses that are integrated by inductor
30
and received by the bridge
14
. The bridge comprises four switches
32
,
34
,
36
,
38
which act in concert to produce an alternating current from the DC pulses.
FIG. 2A
is a diagram showing the switch current in the buck regulator stage of a two-stage power converter in accordance with the prior art, as shown in FIG.
1
.
FIG. 2B
is a diagram showing the inductor current in the buck regulator stage of a two-stage power converter in accordance with the prior art, as shown in FIG.
1
.
FIG. 2C
is a diagram showing the transformer current in a two-stage power converter in accordance with the prior art, as shown in FIG.
1
.
FIGS. 2A
,
2
B and
2
C have equivalent horizontal axes so as to better compare the wave forms.
FIG. 2A
shows the current through switch
20
, which is operating, for example, at 100 Khz. The wave form may be described as a DC pulse train.
FIG. 2B
shows the current through inductor
30
. The wave form may be described as an integrated DC pulse train. The bridge stage
14
requires two DC Current pulses to produce a single cycle of the output 50 KHz AC, as shown in FIG.
2
C.
Since buck regulator stage
12
must produce two pulses of DC power for each cycle of the output frequency, the switch
20
must operate at twice the output AC frequency. Higher switching frequencies at switch
20
generally result in greater power loss and require more expensive switching components. Also, higher currents at inductor
30
generally require more expensive inductor components.
It is therefore desirable to minimize switching power losses, as well as to reduce component costs, in similar circuits.
BRIEF DESCRIPTION OF THE INVENTION
A two-stage high power converter produces a highly regulated DC voltage from unregulated DC input. The first stage, having a plurality of interleaved buck regulators connected in parallel, converts unregulated DC voltage into regulated DC current. The second stage comprises a bridge for receiving the regulated current from the first stage, and converting it into AC voltage, which is in turn applied a step-up transformer. The secondary voltage of the transformer is rectified and filtered to produce low noise DC voltage. A method of converting unregulated DC voltage into regulated DC voltage comprises paralleling a plurality of interleaved buck regulators, where each of the buck regulators includes a switch. Each of the switches is controlled to operate at the same set frequency equal to two times the bridge operating frequency divided by the number of interleaved buck regulators. The combined current from interleaved buck regulators is fed to the bridge.


REFERENCES:
patent: 5132888 (1992-07-01), Lo et al.
patent: 5583753 (1996-12-01), Takayama
patent: 5815386 (1998-09-01), Gordon
patent: 5870296 (1999-02-01), Schaffer
patent: 5886508 (1999-03-01), Jutras
patent: 5894243 (1999-04-01), Hwang
patent: 5929692 (1999-07-01), Carsten
patent: 5959441 (1999-09-01), Brown
patent: 6020691 (2000-02-01), Sun et al.
patent: 6023154 (2000-02-01), Martinez

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