Switching power supply

Details Switching power supply Switching power supply

2002-11-19

2004-06-15

Riley, Shawn (Department: 2838)

Electricity: power supply or regulation systems

Output level responsive

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

Reexamination Certificate

active

06750637

ABSTRACT:

The present disclosure relates to subject matter contained in priority Japanese Patent Application No. 2001-354209, filed on Nov. 20, 2001, the contents of which is herein expressly incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a DC—DC conversion switching power supply, and more particularly relates to a switching power supply including a plurality of DC—DC converters connected in parallel.
2. Description of Related Art
It has been known that a plurality of switching power supplies, or DC—DC converters therefor are connected in parallel to increase their efficiency as well as to decrease the size and weight of a DC—DC conversion switching power supply for supplying medium or high power. Recently, in particular, a type called the “interleave type”—which displaces the phase of a switching current of the switching power supplies, or the DC—DC converters, connected in parallel to one another—is often used to decrease the effective value of an input current, thereby increasing efficiency.
FIG. 34
shows a conventional interleave type switching power supply including triple parallel circuit constitution. In this drawing, the reference numerals
1
a
,
1
b
, and
1
c
respectively denote first, second, and third DC—DC converters, while the reference numerals
1
ai
,
1
bi
, and
1
ci
respectively denote switching current signals of the DC—DC converters
1
a
,
1
b
, and
1
c
. The reference numeral
2
denotes a current mode control circuit, while the reference numerals
21
a
,
21
b
, and
21
c
respectively denote first, second, and third comparators, and the reference numerals
21
ao
,
21
bo
, and
21
co
respectively denote output pulses from the comparators
21
a
,
21
b
, and
21
c
. The reference numeral
22
denotes a detection signal control circuit, while the reference numeral
22
o
denotes a control voltage of the detection signal control circuit
22
. The reference numeral
3
denotes a DC power supply, and
4
denotes a load. While a phase delay circuit for the switching current (which displaces the phases of the switching current of the DC—DC converters
1
a
,
1
b
, and
1
c
) is required for the interleave, details of the phase delay circuit are not necessary for describing this part of the apparatus and are omitted from this drawing.
The current mode control circuit
2
uses the detection signal control circuit
22
to detect output voltages, or output currents, from the DC—DC converters
1
a
,
1
b
, and
1
c
connected in parallel. This creates a controlling output voltage
22
o
which is compared with the switching current signals
1
ai
,
1
bi
, and
1
ci
respectively by the comparators
21
a
,
21
b
, and
21
c
. This results in the individual output pulses
21
ao
,
21
bo
, and
21
co
. These output pulses
21
ao
,
21
bo
, and
21
co
are then used to control operation such that the peaks of the switching current signals
1
ai
,
1
bi
, and
1
ci
of the respective DC—DC converters
1
a
,
1
b
, and
1
c
are equal to the control voltage
22
o
. As a result, the output voltages or currents from the DC—DC converters
1
a
,
1
b
, and
1
c
are controlled so as to be constant.
FIG. 35A
shows the basic waveforms of the control voltage
22
o
, the switching current signals
1
ai
,
1
bi
, and
1
ci
, and the output pulses
21
ao
,
21
bo
, and
21
co
. However, a spike current, and an in-circuit resonance current, flow in the DC—DC converters
1
a
,
1
b
, and
1
c
every time the switching current turns on or off. These DC—DC converters
1
a
,
1
b
, and
1
c
, and the current mode control circuit
2
, are connected to each other at several points including: a detection input of the detection signal control circuit
22
; the input for the switching current signals
1
ai
,
1
bi
, and
1
ci
of the comparators
21
a
,
21
b
, and
21
c
; lines for the output pulses
21
ao
,
21
bo
, and
21
co
, and the line for 0V (or ground). As a result, the spike current and the in-circuit resonance current generated in the DC—DC converters
1
a
,
1
b
, and
1
c
, when turning on and off, can flow into the current mode control circuit
2
through these connection loops.
In addition, when the DC—DC converters
1
a
,
1
b
, and
1
c
, or circuits for driving a switch in the DC—DC converters (
1
a
,
1
b
, and
1
c
), are provided on the same printed circuit board as the current mode control circuit
2
, if their locations and connections are close to one another, the spike current and the in-circuit resonance current generated in the DC—DC converters
1
a
,
1
b
, and
1
c
are often superimposed on signals in the current mode control circuit
2
as a ripple noise, due to electromagnetic induction or the like.
The spike current flowing into the current mode control circuit
2
, and the ripple noise superimposed on the signals in the current mode control circuit
2
, can be considerably reduced by the connection method and the arrangement of the circuits. However, it is difficult to completely eliminate these effects, and they can also be superimposed on the control voltage
22
o
as a ripple noise.
If this is the case, a malfunction can result where the output pulses
21
ao
,
21
bo
, and
21
co
become narrower than their normal pulse width. This is shown in FIG.
35
B. The control voltage
22
o
, on which the ripple noise is superimposed, acts as a switch-on noise or a ripple potential, resulting in a decrease in the control voltage
22
o
. More specifically, when the decrease in the control voltage
22
o
, due to the noise and ripples caused by the turning on and off of the switching current of the other DC—DC converters, occurs within the range of the normal pulse width of the DC—DC converter, the peaks of the switching current signals
1
ai
,
1
bi
, and
1
ci
are compared with the decreased control voltage
22
o
. As a consequence, the width of the output pulses
21
ao
,
21
bo
, and
21
co
decreases.
Additionally, since the detection signal control circuit
22
controls the output voltage or current so as to be constant, narrow pulses caused by malfunction (as above), and wide pulses compensating decreases of the output voltage or current caused by the malfunction, become mixed. The resulting state from this mixing changes depending on conditions of: the input voltage
3
and the load
4
; input/output filter parameters in the DC—DC converters
1
a
,
1
b
, and
1
c
; and the response speed of the detection signal control circuit
22
. Consequently, the ripple component of the output voltage or current fluctuates largely and irregularly compared with the current and voltage characteristics of normal operation. Also, since a switching current with different peaks irregularly flows in inductor components, such as a transformer or a choke in the DC—DC converters
1
a
,
1
b
, and
1
c
, mechanical vibration from gaps in a core, or from insulation tape between windings, generates noise.
As described above, when the plurality of DC—DC converters connected in parallel for a conventional interleave construction are controlled by a single current mode control circuit, the width of the controlling output pulses become narrower due to noise and ripples superimposed on the control voltage
22
o
by the spike current and in-circuit resonance current generated when the switching current in the other DC—DC converters turns on and off. As a result, the ripple component of the output voltage or current fluctuates significantly and irregularly. As a consequence, inductor components in the DC—DC converters, such as the transformer and choke, generate noise.
SUMMARY OF THE INVENTION
In light of the foregoing, an object of the present invention is to provide an interleave type switching power supply which does not generate the malfunction caused by fluctuations of the pulse width, the ripple fluctuation of the output voltage or current, and the noise from the inductor components in the DC—DC converters under the current mode control-with the interleave constitution.
A switching power supply of the pr

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