Electric power conversion systems – Current conversion – With means to introduce or eliminate frequency components
Reexamination Certificate
2001-04-06
2002-09-24
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Current conversion
With means to introduce or eliminate frequency components
C363S131000
Reexamination Certificate
active
06456512
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for PWM (pulse width modulation) frequency correlation, and especially to a method of frequency modulation through PWM for reducing current ripple in a battery.
BACKGROUND OF THE INVENTION
In a general D. C. (direct current) boost circuit, the PWM signal (referring to the wave shapes of G
1
-G
4
of
FIGS. 1 and 2
) outputted from two sets of push-pull PWM controller serves to push the MOSFETs (metal-oxide semiconductor field effect transistor) Q
1
-Q
4
, and then two transformers T
1
and T
2
serve to converter the voltage of a battery into a D. C. high voltage.
In the aforesaid structure, the odd PWM signals G
1
and G
3
are square waves of the same phases which are then inputted to the gates of the MOSFETs Q
1
, Q
3
, while the even PWM signals G
2
and G
4
are square
20
waves of the same phases which are then inputted to the gates of the MOSFETs Q
2
, Q
4
. Then, if the MOSFETs Q
1
-Q
4
are triggered by the PWM signals G
1
-G
4
and then are conducted, the working current flowing into the MOSFETs Q
1
-Q
4
are illustrated as the triangular waves of I
1
-I
4
of
FIG. 2
, while the synthetic current supplied from the battery V BAT is as that shown in I
5
of FIG.
2
.
From the amplitude (
21
) of the synthetic current and the D. C. component, it is known that the ripple is very large. Therefore, the inner resistor of the battery V BAT consumes a large amount of power. Even a filtering capacitor C parallel connected to the battery V BAT is burned. This is a problem can not be overcome.
SUMMARY OF THE INVENTION
Accordingly, the primary object of the present invention is to provide a method for PWM frequency correlation of the present invention is disclosed. In that, 2×M PWM signals G
1
-Gn are supplied to control ends (gates) of the switch elements (such as MOSFET) Q
1
-Qn of the D. C. boost circuit, where M is a prime number larger than 1, and the PWM signals G
1
, G
3
, G
5
, . . . , Gn−1 are synchronous, and have a phase difference of 180 degrees/M, and the PWM signals G
2
, G
4
, G
6
, . . . , Gn are synchronous, and have a phase difference of 180 degrees/M. By this design, a ripple current and EMI interference to the battery as the PWM signal is switched are reduced.
Another object of the present invention is to provide a method for PWM frequency correlation, wherein the ripple component to the battery is reduced effectively and thus, the effect of electromagnetic wave to conductive wires is reduced.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing.
REFERENCES:
patent: 5065300 (1991-11-01), Jacobson et al.
patent: 5479337 (1995-12-01), Voigt
patent: 6292378 (2001-09-01), Brooks et al.
Allis Electric Co., Ltd.
Patel Rajnikant B.
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