Heat management system for a power switching device

A power switching device is provided that includes a housing, a printed circuit board disposed within the housing, and a plurality of electrical components mounted to the printed circuit board, including at least one relay. At least one pair of load terminals is connected to the printed circuit board on opposite sides of the relay, and a plurality of heat transfer elements are formed through and in the printed circuit board and are dispersed proximate the relay, around the load terminals, and extending to the peripheral portion.

FIELD

The present disclosure relates to high current power switching devices, and more particularly to devices and methods for dissipating heat generated by the power switching devices during operation.

BACKGROUND

High current power switching devices often include solid-state switching devices, such as solid-state relay (SSRs) by way of example, which are advantageous because they do not include any moving parts, generate a relatively low amount of electrical noise during operation, are compatible with digital circuitry, and have generally greater switching life. However, solid-state switching devices in the form of solid-state relays produce a relatively high voltage drop during operation, and as a result, generate a substantial amount of heat. This heat must be dissipated during operation to prevent malfunction or failure of the power switching device, and is often achieved through bulky and cost consuming heat sinks.

One known form of such a heat sink includes a thermally conductive body that has a plurality of fins or u-shaped members that extend from a base plate such as those disclosed in U.S. Pat. No. 3,536,960 and U.S. Pat. No. 5,010,050 (also referred to as a “radiator”). These known heat sinks are often bulky, heavy, and introduce additional cost and complexity to power switching device applications.

Other known heat sinks include conductive ceramic base portions, or potting compounds, such as those disclosed in U.S. Pat. No. 4,172,272. As with the finned or u-shaped heat sinks as described above, these compounds or filler materials introduce additional bulk, weight, complexity, and cost to power switching devices. Accordingly, improved devices and methods for enhancing heat transfer are continuously desirable in high current power switching device applications.

SUMMARY

In one form of the present disclosure, a power switching device is provided that comprises a housing and a printed circuit board disposed within the housing, wherein the printed circuit board defines a central portion and a peripheral portion surrounding the central portion. A plurality of electrical components are mounted to the printed circuit board and include at least one relay mounted proximate the central portion. At least one pair of load terminals are connected to the printed circuit board proximate the peripheral portion, and the load terminals are disposed on opposite sides of the relay. A plurality of heat transfer elements are formed through the printed circuit board and are dispersed proximate the relay, around the load terminals, and extend to the peripheral portion.

In another form of the present disclosure, a power switching device is provided that comprises a housing having a plurality of vents and a printed circuit board disposed within the housing, wherein the printed circuit board defines a central portion and a peripheral portion surrounding the central portion. A plurality of electrical components are mounted to the printed circuit board and include at least one relay mounted proximate the central portion. At least one pair of load terminals are connected to the printed circuit board proximate the peripheral portion, and the load terminals are disposed on opposite sides of the relay. A plurality of heat transfer elements are formed through the printed circuit board and are dispersed proximate the relay, around the load terminals, and extend to the peripheral portion.

In yet another form of the present disclosure, a printed circuit board for use in a power switching device is provided that comprises a central portion and a peripheral portion surrounding the central portion. A plurality of electrical components are mounted to the printed circuit board and include at least one relay mounted proximate the central portion. At least one pair of load terminals are connected to the printed circuit board proximate the peripheral portion, and the load terminals are disposed on opposite sides of the relay. A plurality of heat transfer elements are formed through the printed circuit board and are dispersed proximate the relay, around the load terminals, and extend to the peripheral portion.

In still another form of the present disclosure, a power switching device is provided that comprises a housing having a raised portion, stepped portions disposed on opposite sides of the raised portion, and a plurality of vents. A printed circuit board is disposed within the housing, and the printed circuit board defines a central portion and a peripheral portion surrounding the central portion. A plurality of electrical components are mounted to the printed circuit board and include a plurality of relays mounted proximate the central portion and within the raised portion of the housing. A plurality of pairs of load terminals are connected to the printed circuit board proximate the peripheral portion, and the load terminals are disposed on opposite sides of the relays. A plurality of heat transfer elements are formed through the printed circuit board and are dispersed proximate the relay, around the load terminals, and extend to the peripheral portion.

Another form of the present disclosure includes a power switching device that comprises a plurality of high current relays mounted to a printed circuit board and a means for dissipating heat from the high current relays to an outside environment without the use of a heat sink member.

An adapter is also provided in another form of the present disclosure, which is used for mounting a power switching device to a DIN rail. The adapter comprises a body defining a plurality of apertures and a plurality of supports, a release lever operatively engaged with the body and defining a lift portion and a locking portion, a raised lip extending along the body opposite the locking portion of the release lever and adapted for engaging the DIN rail, and a plurality of flexible tabs extending from the body. The release lever operatively moves the locking portion to engage and disengage the DIN rail, and the flexible tabs are adapted to engage and disengage the power switching device

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, a power switching device in accordance with the present disclosure is illustrated and generally indicated by reference numeral10. As shown, the power switching device10comprises a housing12, which in one form includes a base14and a cover16, which are removably engageable with one another as described in greater detail below. The power switching device10also includes a printed circuit board (PCB)20disposed within the housing12with a plurality of electrical components mounted on the PCB2as shown. The electrical components include, by way of example, three (3) relays22a,22b, and22c, which correspond with three-phase operation of the power switching device10. Operation of the power switching device10is described in greater detail in copending application titled “Apparatus and Method for Increasing Switching Life of Electromechanical Contacts in a Hybrid Power Switching Device,” filed on Apr. 30, 2007, which is commonly signed with the present application and the contents of which are incorporated by reference herein in their entirety. It should be understood that the number of relays22illustrated and described herein is merely exemplary and that one (1), two (2), or any number of relays22may be employed while remaining within the scope of the present disclosure. The power switching device10further comprises an adapter30that is adapted for engagement with the housing12and with a DIN rail (not shown), which is described in greater detail below.

Referring now toFIGS. 3aand3b, the PCB20is illustrated in greater detail, including additional electrical components mounted to both sides of the PCB20. The relays22a,22b, and22c(which are electromechanical relays in one form of the present disclosure) are mounted to a top side32of the PCB20, and additional relays23a,23b, and23c(which are solid-state switches such as triacs in one form of the present disclosure) are mounted to a bottom side34of the PCB20. The relays22a,22b,22c,23a,23b, and23care preferably mounted proximate a central portion36of the PCB20as shown.

As further shown, the PCB20also comprises a plurality of load terminals40mounted along or proximate a peripheral portion42of the PCB20. The load terminals40are preferably arranged in pairs and are disposed on opposite sides of the relays22and23, which is best shown inFIGS. 4aand4b. As with the relays22and23, there may be a fewer or greater number of load terminals40than the three (3) pairs illustrated and described herein. Accordingly, the specific number of load terminals40as illustrated and described herein should not be construed as limiting the scope of the present disclosure.

The load terminals40preferably include ring terminals44as shown, which include extensions46(best shown inFIG. 3a) that are adapted to engage features of the housing12to prevent the ring terminals44from turning, which is described in greater detail below. The load terminals40also include corresponding screws47, which engage the ring terminals44to tighten power wire48(only one is shown inFIG. 4afor clarity) to the load terminals40.

Referring now toFIGS. 4a-band5a-c, a plurality of heat transfer elements in the form of nodes50and lands51(shown dashed inFIGS. 4a-b) are formed through and in, respectively, the PCB20in order to transfer the heat generated by the electrical components, and primarily the relays23a,23b, and23c, away from the power switching device10and to the outside environment. As shown, the heat transfer elements50and51are preferably dispersed proximate the relays23a,23b, and23c, around the load terminals40, and extend to the peripheral portion42of the PCB20.

Referring toFIG. 5c, the lands51are sandwiched within the material of the PCB20, and the nodes50extend transversely through the material of the PCB20and the lands51. Furthermore, in one form, linings52are provided between the nodes50and the surrounding material of the PCB20and the lands51for electrical continuity between the top side32and the bottom side34. The linings52and the lands51are preferably a copper material, and are electrically connected to terminals of the relays23a,23b, and23cand also to the load terminals40, among other electrical circuit components. Although the copper lands51reduce electrical resistance and power dissipation, and thus heat generation, the nodes50are provided to further improve heat dissipation. The nodes50are preferably disposed transversely through the copper lands51and the PCB20, and extend to an exterior surface of the PCB20, preferably on both the top side32and the bottom side34as shown.

During operation, a portion of the heat generated by the relays23a,23b, and23c, among other electrical components, is transferred through the heat transfer elements, and more specifically the lands51and the nodes50, to the terminals40, and through both of the housing12(which is described in greater detail below) and the power wires48. As such, the heat transfer elements provide an efficient heat transfer path for the heat generated during operation such that a conventional heat sink member, (e.g., conductive body with fins or u-shaped members, potting compounds), is not required, thus providing a more compact and efficient power switching device10. The heat transfer elements also function to reduce load current path resistance, reduce radiation, and increase thermal conductivity.

In one form, the nodes50are formed by drilling holes through the PCB20and then filling the holes with a conductive filler material. The nodes50preferably comprise a conductive metal filler that is copper, nickel, and gold, and are approximately 0.032 inches (0.013 cm) in diameter as shown in one form of the present disclosure. It should be understood that other types of conductive fillers, such as silver or tin, may also be employed while remaining within the scope of the present disclosure. As long as the material is capable of sufficiently transferring heat away from the relays23a,23b, and23c, and other electrical components, such materials shall be construed as being within the scope of the present disclosure. Furthermore, in one form, the present disclosure avoids the use of lead in order to provide a PCB20that is ROHS compliant. Moreover, shapes other than the circular nodes50as illustrated may also be employed while remaining within the scope of the present disclosure.

As more clearly shown inFIGS. 5aand5b, the nodes50in one form are unevenly distributed across the lands51shown but may also be evenly distributed (not shown) while remaining within the scope of the present disclosure. Within a given distribution, the nodes50in one form are disposed in a general honeycomb pattern54, shown by the dashed line around 6 nodes50. More specifically, the center node50is surrounded by six (6) additional nodes, each of which are spaced 60 degrees apart. Additionally, although the nodes50are illustrated as being the same size, a variety of sizes and shapes may be employed, in addition to other locations throughout the PCB20, while remaining within the scope of the present disclosure. It should also be understood that other types and configurations of heat transfer elements that function to dissipate heat generated by electronic components of the power switching device10may be employed while remaining within the scope of the present invention. For example, heat transfer elements that are not necessary integrally formed within the PCB20may be employed, such as heat transfer elements that are separately and externally attached to the PCB20. Such variations are intended to be within the scope of the present disclosure.

Referring now toFIGS. 6 through 8, the cover16of the housing12is illustrated and now described in greater detail. As shown, the cover16is generally rectangular in shape and comprises a plurality of vents60, which are designed to increase thermal convection and thus the transfer of heat generated by the relays23and other electronic components inside the housing12to the outside environment during operation. In one form, the cover16includes a raised portion62and stepped portions64on opposite sides of the raised portion62. Referring back toFIG. 2, the raised portion62is proximate the relays22and23, and the stepped portions64are proximate the load terminals40. As such, a more compact power switching device10is provided by the shape and design of the cover16as set forth herein.

As shown inFIGS. 1,6, and7, the cover16further comprises terminal access portions70that provide external access to the load terminals40. Therefore, the load terminals40can be accessed by a user without having to remove the cover16. In one form, the terminal access portions70define openings72in the cover16as shown. Preferably, the terminal access portions70are integrally formed with the cover16, but may alternately be provided in the form of removable covers (not shown) while remaining within the scope of the present disclosure. Within the openings72, the cover16further comprises stops74and recesses75(best shown inFIG. 7) that are adapted for engagement by extensions46of the ring terminals44as previously described. Namely, the extensions46of the ring terminals44are disposed within the recesses75, and the stops74prevent the ring terminals44from turning when the screws47are tightened and/or loosened in the load terminals40. In one form, the stops74are integrally formed in the cover16.

The cover16also comprises a plurality of flexible tabs80that include openings82that are adapted to engage features of the base14so that the cover16and the base14are removably engageable with one another. As shown inFIGS. 1 and 9, these features of the base14include external tabs84, which are engaged by the openings82of the flexible tabs80. When the flexible tabs80are displaced outwardly, the openings82disengage from the external tabs84on the base14, and the cover16can then be removed from the base14. When the cover16is placed back over the base14, the flexible tabs80are displaced outwardly such that the external tabs84are positioned proximate the openings82, and then the flexible tabs80are released such that the openings82engage the external tabs84to secure the cover16to the base14.

As further shown, the vents60are formed through the raised portion62, the stepped portions64, and also along the end portions90and92. It should be understood that the vents60can be of a variety of shapes and sizes as shown, and the specific configurations as illustrated herein should not be construed as limiting the scope of the present disclosure.

The cover16also includes cutouts94and spacers96that are configured to accommodate the power terminals98disposed on the PCB20as shown inFIGS. 1,2, and3a. The spacers96preferably extend upwardly from the stepped portion64so as to provide additional dielectric separation between the power terminals98. Both the cutouts94and the spacers96are integrally formed in the cover16in one form of the present disclosure.

Additional features of the cover16include, by way of example, a label area100that can be used to secure a product label with information such as, by way of example, part number, load voltage, amperage, and operating temperature range, among others. Other features, as best shown inFIG. 7, include indicia102as to the load or terminal number, along with appropriate warnings and cautions. Preferably, the indicia102are integrally formed with the cover16, however, other approaches may be employed, such as by way of example, decals or painting, among others. The indicia102as shown are merely exemplary, and thus it should be understood that other indicia102may be employed while remaining within the scope of the present disclosure.

The material for the cover16is preferably electrically nonconductive, and in one form is Ultem® 1000, in order to meet certain operational requirements of the power switching device10such as flammability requirements. It should be understood that other types of thermoplastics and other electrically nonconductive materials may be employed while remaining within the scope of the present disclosure.

Referring now toFIGS. 9 through 11, the base14of the housing12is illustrated and now described in greater detail. The base14generally comprises a rectangular shape to match that of the cover16and includes a cavity110on its upper side surrounded by side walls112and114, and a floor116. A plurality of vents120are formed through the base14, and more specifically through the side walls112and114, and floor116. The vents120are designed to increase the transfer of heat generated by the relays23and other electronic components inside the housing12to the outside environment during operation. In one form, the vents120are partial along the side walls112, and correspond with the vents60along the end portions90and92of the cover16as shown inFIG. 6and inFIG. 1.

The base14further comprises a plurality of mounting flanges122that extend from side walls114. The mounting flanges122include openings123that are provided such that the power switching device10can be mounted to an adjacent structure or to the adapter30(FIGS. 1 and 2), which is described in greater detail below. As further shown, the base14also includes a plurality of ledge portions124disposed within the cavity110that extend from the side walls112. When assembled, the ledge portions124support the PCB20such that the electronic components and the heat generated therefrom are spaced from the floor116in order to increase thermal convection and to provide a path for heat transfer from the PCB20through the vents120and to the outside environment. The side walls114also include flexible tabs126, which snap over the peripheral portion42of the PCB20to secure the PCB20within the base14when assembled.

As further shown, a plurality of standoffs130extend from the floor116and are configured to accommodate the screws47extending from the load terminals40of the PCB20, which are best shown inFIG. 3b. The standoffs130provide additional electrical and thermal isolation between the load terminals40and the electronic components mounted to the PCB20, and also to the outside environment.

Referring toFIG. 11, the bottom of the base14further comprises a plurality of supports132that extend from the floor116to create a standoff between the base14and an adjacent structure such as a DIN rail. Such a standoff further improves thermal convection and heat transfer away from the electronic components of the power switching device10to the outside environment. The bottom of the base14also includes a plurality of apertures134that are configured to receive features of the adapter30, which is described in greater detail below.

Similar to the cover16as previously described, the material for the base14is preferably electrically nonconductive, and in one form is Ultem® 1000, in order to meet certain operational requirements of the power switching device10such as flammability requirements. It should be understood that other types of thermoplastics and other electrically nonconductive materials may be employed while remaining within the scope of the present disclosure.

Referring toFIGS. 12-14, the adapter30is illustrated and is now described in greater detail. The adapter30comprises a body140that defines a plurality of apertures142and a plurality of supports144. A release lever146is operatively engaged with the body140and defines a lift portion148and a locking portion150. On the back side of the adapter30, as best shown inFIGS. 13 and 14, a raised lip152extends along the body140opposite the locking portion150. Furthermore, the adapter30comprises a plurality of flexible tabs154that extend from the body140on the front side, as best shown inFIG. 12. Mounting posts156also extend from the front side of the adapter30, and are configured to engage the apertures134of the base14, which is described in greater detail below.

The raised lip152and the locking portion150of the release lever146are adapted for engaging a DIN rail (not shown), which is positioned between these two features as best shown inFIG. 14. When the lift portion148of the release lever146is lifted by a user in the direction of arrow A, the locking portion150moves in the direction of arrow B to disengage the locking portion150from the DIN rail. When the adapter30is being mounted to the DIN rail, the raised lip152is engaged with one side of the DIN rail, the release lever146is lifted in the direction of arrow A to clear the locking portion150from the other side of the DIN rail, and then the release lever146is released so that the locking portion150engages the DIN rail to secure the adapter30thereto.

Referring back toFIG. 12and also toFIG. 1, the flexible tabs154are adapted to engage and disengage the base14of the housing12through openings123of the mounting flanges122. The flexible tabs154are deflected inwardly to release the power switching device10from the adapter30and are released to engage the power switching device10.

Referring now toFIGS. 11 and 12, the mounting posts156of the adapter30are configured to be received by the apertures134of the base14. Additionally, the mounting posts156are positioned to extend through the openings123in the flanges122of the base16, in order to properly position the power switching device10to the adapter30. With the adapter30, the power switching device10is configured to be mounted horizontally onto a DIN rail or other adjacent structure. The power switching device10may alternately be mounted vertically to a DIN rail or other adjacent structure through the openings123in the flanges122of the base16, without using the adapter30in another form of the present disclosure.

The description of the various embodiments is merely exemplary in nature and, thus, variations that do not depart from the gist of the examples and detailed description herein are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.