Electric power conversion systems – Current conversion – With means to introduce or eliminate frequency components
Reexamination Certificate
2001-12-06
2003-12-09
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Current conversion
With means to introduce or eliminate frequency components
C307S105000, C361S019000
Reexamination Certificate
active
06661680
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a higher harmonic suppressor element for suppressing a higher harmonic and a DC power supply using the same.
2. Description of the Related Art
FIG. 4
shows a circuit diagram of conventional DC power supply unit. The following will describe the prior art with reference to FIG.
4
.
The conventional DC power supply unit
50
is comprised of an AC power supply
52
, a voltage selection switch
54
for selecting either one of a 100-V AC voltage and a 200-V AC voltage applied by the AC power supply
52
, a rectifying/smoothing circuit
56
for rectifying and smoothing a 100-V AC voltage by the double voltage rectification method if it is selected by the voltage selection switch
54
and rectifying and smoothing a 200-V AC voltage by the equi voltage rectification method if it is selected by the voltage selection switch
54
, and a higher harmonic coil
58
which is interposed between the AC power supply
52
and the rectifying/smoothing circuit
56
only when a 200-V AC voltage is selected by the voltage selection switch
54
.
The DC power supply unit
50
further includes a filter circuit
60
for canceling noise from an AC voltage, wherein the filter circuit
60
is interposed between the higher harmonic coil
58
and the AC power supply
52
. The filter circuit
60
is of a typical type including a coil, a capacitor and a resistor. On an output side of the rectifying/smoothing circuit
56
is provided with a supply voltage control circuit
62
for controlling an output voltage at a constant value. The supply voltage control circuit
62
is a typical type including a switching transistor, an output transformer, a capacitor, a resistor.
The rectifying/smoothing circuit
56
is comprised of bridge-connected rectifying diodes
561
-
564
and a pair of serial-connected smoothing capacitors
565
and
566
. The voltage selection switch
54
is connected between an interconnection point of the capacitors
565
and
566
and one output terminal of the filter circuit
60
. The higher harmonic coil
58
has such a frequency characteristic that suppresses a higher harmonic.
The commercially available AC power supply
52
comes in a 100-V type or a 200-V type. To use the 200-V AC power supply
52
, the voltage selection switch
54
is opened. In this case, a positive half-wave of the AC voltage flows through the higher harmonic coil
58
, the diode
563
, the capacitor
565
, the capacitor
566
, and the diode
562
in this order, while a negative half-wave thereof flows through the diode
564
, the capacitor
565
, the capacitor
566
, the diode
561
, and the higher harmonic coil
58
in this order. That is, the 200-V AC voltage is rectified and smoothed by the equi voltage rectification method.
To use the 100-V AC power supply
52
, on the other hand, the voltage selection switch
54
is closed. In this case, the positive half-wave flows through the voltage selection switch
54
, capacitor
566
, the diode
562
in this order, while the negative half-wave flows through the diode
564
, the capacitor
565
, and the voltage selection switch
54
in this order. That is, a 100-V AC voltage is rectified and smoothed by the double voltage rectification method. Thus, the DC power supply unit
50
gives the same output voltage irrespective of which one of the 100-V and 200-V AC power supplies
52
is used.
Suppose that the voltage selection switch
54
is opened mistakenly when the 100-V AC power supply
52
is used. Then, the rectifying/smoothing circuit
56
rectifies and smoothes a 100-V AC voltage according to the equi voltage rectification method not according to the double voltage rectification method. This causes the supply voltage control circuit
62
to keep the switching transistor ON in an attempt to maintain a predetermined output voltage, thus flowing a mass current to the rectifying/smoothing circuit
56
. As a result, an over-current flows also to the higher harmonic coil
58
, which is overheated or smokes.
Even when the voltage selection switch
54
is properly set, on the other hand, a short-circuit current may occur owing to a fault or abnormality in the rectifying/smoothing circuit
56
or the supply voltage control circuit
62
. In this case also, an over-current flows to the higher harmonic coil
58
, which is overheated or smokes.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide a higher harmonic suppressor element that can prevent an over-current from flowing to a higher harmonic coil and a DC power supply using the same.
The higher harmonic suppressor element according to the present invention comprising: a higher harmonic coil for suppressing the higher harmonic; a thermal fuse which is connected in series with said higher harmonic coil and also which is melted down by heat generated by said higher harmonic coil. And said higher harmonic coil is contained in an envelope body along with said thermal fuse. Further more, said higher harmonic coil is equipped with a magnetic core and a winding wound around said magnetic core in such a configuration that said thermal fuse is in contact with said magnetic core.
If an over-current flows to the higher harmonic coil, it generates heat to thereby melt down a thermal fuse. With the melting down of the thermal fuse, which is connected in series with the higher harmonic coil, the over-current flow to the higher harmonic coil is cut.
Moreover, a DC power supply unit according to the present invention comprising: a rectifying/smoothing circuit for rectifying and smoothing an AC voltage applied from an AC power supply and the higher harmonic suppressor element which is interposed between said AC power supply and said rectifying/smoothing circuit, wherein the higher harmonic suppressor element including a higher harmonic coil for suppressing a higher harmonic and a thermal fuse which is connected in series with said higher harmonic coil and also which is melted down by heat generated by said higher harmonic coil.
An over-current may flow to the higher harmonic coil owing to a fault or abnormality on the downstream side of the rectifying/smoothing circuit. If an over-current flows to the higher harmonic coil, it runs hot to thereby melt down the thermal fuse. With the melting down of the thermal fuse, which is connected in series with the higher harmonic coil, the over-current flow to the higher harmonic coil is cut.
Further more, a DC power supply unit according to the present invention comprising: a voltage selection switch for selecting either one of a first AC voltage and a second AC voltage which is twice as high as said first AC voltage, wherein each voltage applied from an AC power supply; a rectifying/smoothing circuit for rectifying and smoothing said first AC voltage by the double voltage rectification method if said first AC voltage is selected by said voltage selection switch and, if said second AC voltage is selected by said voltage selection switch, rectifying and smoothing said second AC voltage by the equi voltage rectification method; and
the higher harmonic suppressor element which is interposed between said AC power supply and said rectifying/smoothing circuit only when said second AC voltage is selected by said voltage selection switch, wherein the higher harmonic suppressor element including a higher harmonic coil for suppressing a higher harmonic and a thermal fuse which is connected in series with said higher harmonic coil and also which is melted down by heat generated by said higher harmonic coil.
An over-current may flow to the higher harmonic coil owing to a mistake in setting of the voltage selection switch or an abnormality on the downstream side of the rectifying/smoothing circuit. If an over-current flows to the higher harmonic coil, it runs hot to melt down the thermal fuse. With the melting down of the thermal fuse, which is connected in series with the higher harmonic coil, the over-current flow to the higher harmonic coil is cut.
REFERENCES:
patent: 3927350 (1975-1
Katten Muchin Zavis & Rosenman
NEC Corporation
Patel Rajnikant B.
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