Inductor devices – Coil or coil turn supports or spacers – Printed circuit-type coil
Reexamination Certificate
2000-02-23
2001-08-28
Mai, Anh (Department: 2832)
Inductor devices
Coil or coil turn supports or spacers
Printed circuit-type coil
C336S223000, C336S232000
Reexamination Certificate
active
06281779
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coil device such as a transformer and an inductor to be used for electronic equipment, switching power supply apparatus or the like, and the switching power supply apparatus using it.
2. Description of the Related Art
Switching power supply apparatus have been widely used for a power supply units of various electronic devices such as personal computers, facsimile machines or the like. Especially, switching power supply apparatus including an isolated forward converter type as a DC-DC converter are suitably employed in laptop computers or the like.
Such a switching power supply apparatus including an isolated forward converter generally comprises a power transformer, a driving transformer and a choke coil. These coil elements use coils and core parts, which are bulky and require substantial spaces to be mounted on a circuit board. As a result, it is very difficult to miniaturize the circuit board and switching power supply apparatus itself.
In addition, transformers and choke coils are relatively expensive elements due to the fact that manufacturing methods of these elements include a step which cannot be automatically processed. It is difficult to reduce the cost of the switching power supply apparatus, accordingly.
SUMMARY OF THE INVENTION
The present invention can solve the aforementioned drawbacks associated with the conventional coil elements and provides a coil device capable of saving space, miniaturizing size, and reducing cost. The present invention also provides a switching power supply apparatus which uses the coil device and can be produced at a low cost.
The coil device comprises a core, first printed coil and a second printed coil. The core has an intermediate leg and at least a pair of external legs arranged with equal intervals from the intermediate leg. The first printed coil is provided on a first substrate which has an intermediate hole and a pair of external holes respectively inserted in the intermediate leg and the pair of external legs of the core, the first printed coil being wound around the intermediate hole. The second printed coil is provided on a second substrate which has an intermediate hole and a pair of external holes respectively inserted in the intermediate leg and the pair of external legs of the core, the second printed coil including a pair of external printed coils which are connected in series and are respectively wound around the pair of the external holes by the same number of turns but in the opposite directions.
According to this structure, the pair of external printed coils of the second printed coil generate magnetic fields in the opposite direction to each other in the intermediate leg such that the magnetic fields are canceled with each other and induce no induction voltage in the first printed coil, and induction voltages induced in the external printed coils of the second printed coil by the magnetic flux generated by the first printed coil is canceled to be equivalently 0V, whereby the first printed coil and the second printed coil form separate inductors which are not magnetically coupled.
In this invention, the number of total legs of the core includes three for a pair of external legs to one intermediate legs, four in the case of a pair of external legs and one external leg, or five in the case of two pairs of external legs.
First, a case where the number of total legs of the above-described core is three, is described. The case where the number of total legs is three is of the structure where a pair of external legs are arranged with equal intervals with the intermediate leg as the base point. Thus, a conventional E-shaped core in which the external legs are arranged in the direction opposite to each other by 180° with the intermediate leg as the center is included in this case of three legs.
Among a pair of external legs, one external printed coil wound around the one external leg and the other external printed coil wound around the other external leg are wound in the same direction and inversely connected in series, or wound in the reverse direction and forwardly connected in series to form one second printed coil (a pair of external printed coils).
Thus, when current flows in the first printed coil (intermediate printed coil) wound around the intermediate leg, magnetic fluxes parallel in the same direction passing through the one external leg and the other external leg are generated. The voltages induced in the one external printed coil and the other printed coil to be interlinked with the magnetic fluxes are in the opposite direction to each other, and canceled, and no equivalently induced voltages are outputted in both terminals of the second printed coil (a pair of external printed coils).
When current flows in the second printed coil (a pair of external printed coils), the magnetic fluxes which are generated from the one external printed coil and the other external printed coil and pass through the intermediate leg are in the opposite direction to each other, and cancel each other, and no induced voltage is outputted in both terminals of the first printed coil (intermediate printed coil).
Thus, the first printed coil (intermediate printed coil) wound around the intermediate leg and the second printed coil (a pair of external printed coils) wound around a pair of external legs constitute coil devices which are individual parts wound by cores as if they are independent from each other where the core is commonly used, and the interlinked magnetic fluxes or the induced voltages cancel with each other.
Second, a case where the number of total legs of the above-described core is four is described. In the case of four legs, which is a case where one leg (the fourth leg) is added to the above-described case with three legs, and the fourth leg is arranged on a line to perpendicularly divide into two the line connecting the external legs of a pair of external legs to each other. Thus, the fourth leg is in a relationship similar to that of the above-described intermediate leg in the form relative to a pair of external legs, and at the same time, similar to that of the above-described intermediate leg, in effect, so to speak, the second intermediate leg. Further, the fourth leg forms the relationship of a U-shaped core in relation to the intermediate leg, and the printed coils wound therearound forms the relationship between the primary coil and the secondary coil. The external printed coil wound around the fourth leg is paired with the intermediate printed coil wound around the intermediate leg, that is, a similar relationship to that of a pair of above-described external printed coils can be formed by connecting the printed coils in series so that the directions of the magnetic fluxes passing through the legs become opposite to each other. Two pairs of external printed coils can be formed thereby. In addition, two transformers can be formed by forming two pairs of external printed coils equivalent or similar to each other.
Third, a case where the number of total legs of the above-described core is five is described. In the case of five legs, which is a case where two sets of a pair of external legs, i.e., two pairs of external legs are provided, and the effect of two pairs of external printed coils (two second printed coils) wound around two sets of the external legs to the intermediate leg is the same as the relationship between the above-described intermediate leg and a pair of the external printed coils (one second printed coil). Further, the relationship between two sets of the external printed coils, i.e., between a pair of one external printed coils and a pair of the other printed coils is that the mutually induced voltages equivalently cancel each other.
Further, a case where the number of total legs is six or more is possible, and the description for the above-described cases of three to five legs is analogously applicable.
According to another embodiment of the invention, the coil device is further provided with a third printed c
Matsumoto Tadahiko
Nagai Jun
Mai Anh
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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