US20090065174A1

US20090065174A1 - Heat sink for an electrical device and method of manufacturing the same

Info

Publication number: US20090065174A1
Application number: US11/898,090
Authority: US
Inventors: Yu-Jen Lai; Song-Kai Su
Original assignee: Phoenixtec Power Co Ltd
Current assignee: Phoenixtec Power Co Ltd
Priority date: 2007-09-10
Filing date: 2007-09-10
Publication date: 2009-03-12

Abstract

A heat sink for an electrical device has a frame and at least one fin. The frame has an inner chamber. The fin is mounted in the inner chamber of the frame to separate the inner chamber of the frame into at least two channels. Therefore, heat generated from any electrical element connected to or mounted on the heat sink will transfer evenly to the heat sink. The heat sink not only dissipates heat evenly, but also provides multiple channels to dissipate heat by convection. Because the heat sink only has one frame, assembly of an electrical device is easy and quick.

Description

BACKGROUND OF THE INVENTION

1. Field of Invention
The present invention relates to a heat sink used in electrical devices, and more particularly to a heat sink used in an un-interruptible power supply (UPS), which is assembled easily and has excellent efficiency of heat dissipation.
2. Description of the Related Art
Electrical devices, such as an un-interruptible power supply (UPS), require excess heat to be removed leading to the development of heat sinks.
Conventional methods of dealing with the excess heat are such as selecting low heat generating elements, enlarging the heat sink or increasing the fans to remove the heat out of the device. Apparently, the methods have the disadvantage such as increasing the cost, enlarging the size, and decreasing the performance. Each of said methods goes against the object of the high power density and miniaturization, so the best method is improving the efficiency of the heat dissipation.
The heat sink of the electrical device is made of extruded aluminum and has a surface area and fins that enlarge the surface area to reduce heat in the electrical device according to a basic overall heat-transfer equation:
Q=UA _t(T _ave −T _∞)
Wherein

- Q is heat transfer rate;
- U is overall heat transfer coefficient;
- A is the surface area of the heat sink;
- T_aveis an average temperature in a surface of the heat sink;
- T_∞ is a temperature of environment.

With reference to FIGS. 5 and 6, a UPS (1′) has a front panel, a rear panel, a fan (20), a conventional heat sink (30) and electrical elements. The fan (20) is mounted on the rear of the UPS (1′). The heat sink (30) is mounted in the UPS (1′), and has two symmetrical frames (31). Each frame (31) is U-shaped, faces the other frame to form a parallelepiped with an inner chamber and has two sides and several fins (33).
The fins (33) are parallel extruded from the frame (31) and have two surfaces that increase a surface area of the heat sink (30). The electrical elements are mounted onto the frame (31), to allow the generated heat to be easily transferred to the fins (33) and removed by convection increased by the airflow forcing by the fan (20). Therefore, the generated heat can be removed out of the UPS (1′).
However, all of the electrical elements mounted on the two frames (31) do not be activated together. Because of the limitation of design, usually only the electrical elements on the same frame are activated in the same time, it rises the temperature of the frame. But the other frame keeps a low temperature comparatively, because of the electrical elements mounted on it aren't activated in the same time. As a result, the whole heat sink (30) hasn't a unit temperature, the other frame can't be used completely, so the total efficiency of the heat dissipation decreased.
To overcome the shortcomings, the present invention provides a heat sink for electrical device to mitigate or obviate the aforementioned.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a heat sink used in an electrical device, which is assembled easily and has a high performance to dissipate the excess heat.
To achieve the objective, the heat sink for an electrical device in accordance with the present invention has a frame and at least one fin. The frame has an inner chamber. The fin is mounted in the inner chamber of the frame to separate the inner chamber of the frame into at least two channels. Therefore, heat generated from any electrical element mounted on the heat sink will transfer evenly to the heat sink of. The heat sink not only spreads heat evenly, but also provides multiple channels to dissipate the excess heat by convecting with the airflow. Besides, the heat sink only has one frame, so assemble the heat sink with the electrical device will be much easier and quicker.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description of the preferred embodiment of the invention illustrated in the accompanying drawings, wherein:

FIG. 1 is a perspective view of a heat sink in accordance with the present invention;

FIG. 2 is a front view of the heat sink in FIG. 1;

FIG. 3 is a perspective view of the heat sink in FIG. 1 mounted in an un-interruptible power supply;

FIG. 4 is a side view of the heat sink in FIG. 3;

FIG. 5 is a perspective view of a conventional heat sink in accordance with the prior art; and

FIG. 6 is a perspective view of the conventional heat sink in FIG. 5 mounted in an un-interruptible power supply.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 and 3, a heat sink (10) in accordance with the present invention is used in an electrical device (1) and has a frame (11) and at least one fin (12).
The frame (11) may be a parallelepiped, may be made of extruded aluminum and has an inner chamber. A rectangular frame (11) has a width of 62 millimeters (mm), a height of 58 millimeters (mm), two mounting sides (14) and two non-mounting sides (15). The mounting sides (14) are defined opposite to each other and may be 4.1 mm thick. The non-mounting sides (15) are defined opposite to each other, are perpendicular to the mounting sides (14) and may be 2.3 mm thick.
With further reference to FIG. 2, the at least one fin (12) is mounted in the inner chamber of the frame (11) to separate the inner chamber of the frame (11) into at least two channels (13). When six fins (12) are mounted in the inner chamber, the fins (12) are mounted at intervals and each interval is 6 mm thick. The at least one fin (12) may be aluminum extruded from the frame (11) and may be rectangular. Each rectangular fin (12) has two edges. The edges of the fin (12) connect respectively to the mounting sides (14) of the rectangular frame (11) to form at least two channels (13). Each rectangular fin (12) is 1.9 mm thick. Preferably, six rectangular fins (12) are used. The channels (13) are formed in the frame (11).
With further reference to FIG. 3, the electrical device (1) may be an un-interruptible power supply (UPS) and has a front, a rear, the heat sink (10) of the present invention, at least one ventilating device, a bracket (50) and a printed circuit board (PCB) (51).
The heat sink (10) is mounted on the PCB (51)
The at least one ventilating device (20) communicates with the channels (13) of the heat sink (10) and forces air to flow through the channels (13) of the heat sink (10) to increase the dissipation efficiency of the heat sink (10). The ventilating device (20) may be a fan. The ventilating device (20) is mounted on the rear of the UPS (1) and may be mounted on the frame (11) of the heat sink.
The bracket (50) is mounted between the front and rear and has two connecting edges and two surfaces. The connecting edges are respectively connected to the front and rear of the UPS (1).
The PCB (51) is mounted to the bracket (50) and allows one of the non-mounting sides (15) of the frame (11) to be mounted on the PCB (51). Therefore, the heat sink (10) can be mounted or easily connected indirectly to the PCB. The PCB (51) comprises a first group of electrical elements and a second group of electrical elements.
With further reference to FIG. 4, the first group of the electrical elements is mounted on one mounting side (14) of the frame (11) of the heat sink (10) and has multiple DC/DC metal-oxide-semiconductor field-effect transistors (DC/DC MOSFET) (41, 41 a) and a rectifier (42). The DC/DC MOSFETs (41, 41 a) are mounted on one mounting side (14) of the frame (11) of the heat sink (10) from the front to near the rear of the UPS (1), and the DC/DC MOSFET nearest the rear being the first DC/DC MOSFET (41 a). The rectifier (42) is mounted on the side of the frame (11) on which the DC/DC MOSFETs (41, 41 a) are mounted, is adjacent to the first DC/DC MOSFET (41 a) at the rear of the UPS (1). The second group of the electrical elements is mounted on the other mounting side (14) of the frame (11) of the heat sink (10) and has a first power factor correction diode (PFC diode) (43), a second PFC diode (44), a first inverter insulated gate bipolar transistor (IGBT) (45) and a second inverter IGBT (46). The first PFC diode (43), the second PFC diode (44), the first inverter IGBT (45) and the second inverter IGBT (46) are respectively mounted on the frame (11) of the heat sink (10) from the front to the rear of the UPS (1).
While AC input power is normal, the UPS (1) will work in the Line Mode, the rectifier (42), the PFC diode (43), the second PFC diode (44), the first inverter IGBT (45) and the second inverter IGBT (46) will be activated.
While AC input power is abnormal, the UPS (1) will use the backup DC power and work in the Battery Mode, all the DC/DC MOSFETs (41, 41 a), the first inverter IGBT (45) and the second inverter IGBT (46) will be activated.
Heat generated from any electrical elements will transfer evenly to the heat sink (10). The ventilating device increases airflow and the heat can be dissipated quickly and efficiently.
A method of manufacturing the heat sink for the electrical device in accordance with the present invention, comprises two steps:
a) step comprises making a frame which has an inner chamber, two mounting sides and two non-mounting sides. The mounting sides are defined as opposite to each other and are used for mounting generating heat electrical elements. The non-mounting sides are defined as opposite to each other and at least one of them is used for fastening the heat sink to the electrical device.
b) step comprises mounting at least one fin in the inner chamber of the frame to separate the inner chamber of the frame into at least two channels. Each fin has two edges that are connected respectively to the two mounting sides of the frame.
Examples: These experiments compare an efficiency of the heat sink (10) of the present invention with a conventional heat sink.
Test 1.
AC power is supplied to the UPS (1) at 170 volts until the electrical elements hold a steady temperature. Some electrical elements mounted on the heat sink of the present and the conventional heat sink are measured, as shown in Table 1:

TABLE 1

	Conventional		Temperature
Electrical	heat sink	Present invention	difference
element	(T/° C.)	(T/° C.)	(T/° C.)

PFC diode (43)	66.7	49.4	−17.3
Second PFC diode (44)	67.2	54.3	−12.9
First inverter IGBT (45)	75.1	63	−12.1
Second inverter IGBT	73	66.7	−6.3
(46)
First DC/DC MOSFET	52.1	50.3	−1.8
(41a)
Rectifier (42)	64.9	69.4	+4.5

Text 2.
After test 1, DC power is supplied from a battery to the UPS (1) and the UPS work in Battery Mode for 30 minutes. The temperatures of some of the electrical elements mounted on the heat sink of the present and the conventional heat sink are measured, as shown in Table 2:

TABLE 2

	Conventional		Temperature
Electrical	heat sink	Present invention	difference
element	(T/° C.)	(T/° C.)	(T/° C.)

First DC/DC MOSFET	93.8	78.1	−15.7
(41a)
Rectifier (42)	79.5	70.9	−8.6

Test 3.
After test 2, AC power is supplied to the UPS (1) at 272 volts. Temperatures of some electrical elements mounted on the heat sink of the present and the conventional heat sink are measured, as shown in Table 3:

TABLE 3

	Conventional		Temperature
Electrical	heat sink	Present invention	difference
element	(T/° C.)	(T/° C.)	(T/° C.)

PFC diode(43)	59.9	47.1	−12.8
Second PFC diode (44)	60.6	51.4	−9.2
First inverter IGBT (45)	67.3	59.7	−7.6
Second inverter IGBT	65.1	61.4	−3.7
(46)
First DC/DC MOSFET	49.8	47.3	−2.5
(41a)
Rectifier (42)	50.3	49.7	−0.6

According to the foregoing tables, the heat sink (10) of the present invention efficiently dissipates heat. Therefore, the heat sink (10) of the present invention not only transfers heat evenly, but also provides multiple channels (13) to dissipate heat by convection. Additionally, because the heat sink (10) only has one frame (11), the heat sink (10) can reduces assembly time and difficulty of the electrical device (1).
Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A heat sink for an electrical device comprising

a frame, having

an inner chamber;

two mounting sides being defined as opposite to each other and being adapted to allow generating heat elements of the electrical device to be mounted on the mounting sides; and

two non-mounting sides being defined as opposite to each other and at least one of the non-mounting sides allowing the heat sink to be fastened to the electrical device;

at least one fin mounted in the inner chamber of the frame to separate the inner chamber of the frame into at least two channels and each fin having two edges being connected respectively to the two mounting sides of the frame.

2. The heat sink for an electrical device as claimed in claim 1, wherein each fin is rectangular.

3. The heat sink for an electrical device as claimed in claim 2, wherein

the frame is made of extruded aluminum; and the at least one fin is aluminum extruded from the frame.

4. The heat sink for an electrical device as claimed in claim 1, wherein said electrical device is an UPS.

5. A method of manufacturing a heat sink for an electrical device comprising steps of:

a) making a frame which has

an inner chamber;

two mounting sides being defined as opposite to each other and being used for mounting generating heat electrical elements; and

two non-mounting sides being defined as opposite to each other and at least one of them being used for fastening the heat sink to the electrical device; and

b) mounting at least one fin in the inner chamber of the frame to separate the inner chamber of the frame into at least two channels and each fin having two edges being connected respectively to the two mounting sides of the frame.

6. The method of claim 5, wherein the frame is a parallelepiped.

7. The method of claim 5, wherein each fin is rectangular.

8. The method of claim 6, wherein each fin is parallel with the two non-mounting sides of the frame.

9. The method of claim 5, wherein

the frame is made of extruded aluminum; and

the at least one fin is aluminum extruded from the frame.