Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-11-23
2001-04-24
Picard, Leo P. (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S704000, C174S050510, C257S707000, C165S080300
Reexamination Certificate
active
06222733
ABSTRACT:
The present invention concerns a device and a method for cooling a planar inductance coil, in particular a planar transformer, on a plate-shaped support having a plurality of conducting layers, wherein at least one conducting layer of the support, in co-operation with a core element designed to guide a magnetic flux, represents the planar inductance coil.
A typical area of use of devices of that kind, of the general kind set forth, are switching power supplies. In this context, due to increasing miniaturization, multi-layer support plates (referred to as “multi-layer” members) are increasingly used, which have a plurality of conducting layers within a conventional circuit board structure, the conducting layers being electrically separated from each other or being connected in point configuration. In this area of use for example also conventional discrete inductance coils such as for example transformers or chokes are being afforded by use of the planar technology, more specifically by directly utilizing suitably designed conducting layers of the multi-layer member as windings of that inductance coil, in which case they then usually co-operate with a transformers core which is suitably placed on the multi-layer member or in openings therethrough.
The use of such planar inductance coils of the general kind set forth is however made difficult in particular in regard to power electronics by a number of mechanical and thermal problems. Thus more specifically for example in switching power supplies in a very small space copper and core losses are incurred, which without particular cooling measures cause an excessive rise in temperature of the multi-layer conductor supports so that even for example when over-dimensioning is involved the use of this novel technology encounters power limits.
Particularly in the case of devices with a relatively high level of (lost) power therefore attempts have been made to additionally cool the multi-layer member by various measures, with for example so-called “thermal drains”, that is to say heat sinks, in the form of metal pins or the like, being used in relation to a cooling body. An arrangement of that kind, which is to be found in the state of the art, is illustrated for the sake of simplicity in
FIG. 4
of the accompanying drawing: a transformer arrangement or choke in a multi-layer member
10
with conducting layers which are designed accordingly as transformer windings has a first transformer core
12
which for example is of an E-shaped configuration in cross-section and which extends with limbs
14
through corresponding openings in slot form in the multi-layer member
10
. To close the magnetic circuit, disposed on the first transformer core
12
is a second plate-shaped transformer core
16
which is of an I-shaped configuration in cross-section so that winding layers which extend for example in the interposed multi-layer portions
18
are embraced by the transformer core
12
,
16
. The core elements
12
,
16
are glued together in lateral relationship or in surface relationship and thus guarantee the magnetic circuit.
To cool this arrangement—which as stated is known from the state of the art—shown in the left-hand region of
FIG. 4
is a spacer pin
20
which is pressed into the board or plate
10
and which at the other end affords thermal contact with a plate-shaped cooling body
22
. An alternative which is also known from the state of the art is shown in the right-hand region of
FIG. 4
; in that case, a cooling pin
24
is soldered directly into the board
10
and—like also the spacer pin
20
—connected to the cooling body
22
by means of a screw connection.
Such an arrangement however gives rise to a series of damaging safety and thermal expansion problems and furthermore space is additionally required on the circuit board
10
due to the thermal transfer and spacer portions
20
,
24
respectively. The rigid connection involved is also unsatisfactory and liable to trouble, in particular in relation to acceleration phenomena or in the event of a severe mechanical loading. A further disadvantage is that the heat is only dissipated in punctiform fashion by the thermal drains and furthermore the through holes which are required for that purpose reduce the usable surface area of the multi-layer member even for the internally disposed layers.
A further approach which is to be found in the state of the art is illustrated in
FIG. 5
, showing thermal bonding of the transformer core itself to the cooling body
22
. That is effected by means of an elastic layer
26
of heat-conducting material which is disposed between the transformer core
16
and the cooling body
22
in the manner shown in FIG.
5
. The mechanical connection between the cooling body
22
and the multi-layer member
10
is afforded by way of spacer portions
28
and screws
30
; the dimensional tolerances which naturally occur in respect of the cores and bolts however necessitate flexibility on the part of the material
26
which, in the form of a flexible heat-conducting mat of large area, is also referred to as a “gap pad” or “soft pad”. Besides heat dissipation to the cooling body still being unsatisfactory, due to the transfer conditions involved, the arrangement shown in
FIG. 5
therefore also gives rise to not inconsiderable production and manufacturing expenditure. The
FIG. 5
arrangement also suffers from the same disadvantages as the construction shown in FIG.
4
.
Finally,
FIG. 6
shows a further approach to be found in the state of the art, in which heat of the multi-layer member
10
is discharged to the cooling body
22
by means of elastic heat-conducting mats
32
; at the same time the transformer arrangement can be held by a resilient clip element
34
. This arrangement however does not involve any cooling of the core.
All those arrangements however give rise to a not inconsiderable level of expenditure and in addition are in particular not suitable for the dissipation of relatively large amounts of heat, governed by the power involved. Furthermore this state of the art does not provide for any fixing of the core; if necessary such fixing would have to be implemented separately.
The severity of that problem is increased when planar transformers are used in a so-called matrix arrangement; a plurality of transformers which are arranged in a distributed array on a multi-layer member and which each require individual local heat dissipation.
Finally, there would in principle also be the possibility of sealing a transformer arrangement on a multi-layer member with a heat-conducting casting material in order in addition to cool the arrangement. The poor testability and reparability of this arrangement however is evident here, as well as the basically rather poor suitability of casting materials for dissipating heat; in addition cores and further components are subjected to mechanical loadings.
Therefore the object of the present invention, for multi-layer supports of the general kind set forth, with fitted planar inductors, is to provide a heat dissipation means which is in particular even suitable for high levels of power loss and which is mechanically stable and which in addition permits simple, inexpensive and potentially automatable production.
That object is attained by the apparatus set forth in claim
1
and the use as set forth in claim
9
; advantageous developments of the invention are set forth in the appendant claims. Advantageously the invention makes it possible to provide a planar inductance coil in a multi-layer member, in particular a circuit arrangement in power electronics, which is extremely simple in terms of manufacture, which is suitable for automatic fitment or implementation and which in addition permits a very high degree of heat dissipation—both from the heat-generating portion of the multi-layer member and also from the transformer core.
In accordance with the invention it has been found that the direct and immediate connection of the cooling element which has a planar contact surface to the core element allows arrangements wit
Carter & Schnedler, P.A.
Datskovsky Michael
Melcher A.G.
Picard Leo P.
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