Patent Application
20230108943
The present application claims the priority to Chinese Patent Application No. 202020837107.2, titled “POWER CONVERSION APPARATUS”, filed on May 19, 2020 with the China National Intellectual Property Administration, which is incorporated herein by reference in its entirety.
The present disclosure relates to the technical field of heat dissipation in power electronics, and in particular to a power conversion apparatus.
In various application scenarios, a system not only requires a power conversion apparatus to meet a rated condition, but also requires the power conversion apparatus to provide an output capacity several times higher than a peak in the rated condition in a short period of time. In this case, loss of a heating element in the power conversion apparatus increases exponentially, resulting in a great impact on devices such as a power semiconductor device in the power conversion apparatus.
The power semiconductor device, for example, a wafer, is small in size, and is to be industrially packaged in order to be made into a finished product, thus the finished product is also small in size. In addition, in an electrical apparatus, the power semiconductor device is isolated from a heat dissipation device by an insulating material for the sake of electrical insulation, and the insulating material generally has a poor thermal conductivity. Therefore, a great loss of the power semiconductor device in a short period of time inevitably results in a sharp rise in a temperature of the power semiconductor device, greatly impacting the power semiconductor device and further reducing operation reliability of the system.
At present, in order to solve the above problems, a switch transistor with high performance is generally adopted or multiple switch transistors are connected in parallel to reduce power consumption at the peak, thereby reducing a rate at which the temperature of the power semiconductor device rises. Alternatively, the insulating material is replaced with a material of a high thermal conductivity, such as an aluminum substrate and a thermally conductive silicone grease, to speed up heat transfer from the power semiconductor device to the heat dissipation device. Alternatively, a heat dissipation device with a high heat dissipation capacity may be adopted to reduce the temperature of the power conversion apparatus itself.
However, there is a problem that the system is large in size and weight, and has high costs existing in all of the above existing technical solutions.
In view of this, a power conversion apparatus is provided according to an embodiment of the present disclosure, to solve the problem existing in the conventional technology that the system is large in size and weight, and has high costs.
To achieve the above object, the following technical solutions are provided according to embodiments of the present disclosure.
A power conversion apparatus is provided according to the present disclosure. The power conversion apparatus includes: a low thermal resistance path, a high thermal resistance path, a heatsink, an additional high heat capacity device, and at least one heating element. The additional high heat capacity device is connected to the at least one heating element via the low thermal resistance path. The heatsink is connected to the at least one heating element via the high thermal resistance path.
In an embodiment, the low thermal resistance path is made of one kind of metal or multiple kinds of metal.
In an embodiment, the additional high heat capacity device is made of metal.
In an embodiment, the additional high heat capacity device is made of copper or aluminum.
In an embodiment, the additional high heat capacity device is in a shape of a strip or a block.
In an embodiment, the additional high heat capacity device is arranged around the at least one heating element, or the additional high heat capacity device is arranged to straddle the at least one heating element.
In an embodiment, each of the at least one heating element includes a power device chip arranged on a chip lead frame.
In an embodiment, the low thermal resistance path is formed by a surface metal of a PCB and solder for the surface metal. Multiple heating elements form a power conversion circuit on the PCB.
In an embodiment, the power conversion circuit is an ACDC conversion circuit, a DCAC conversion circuit, a DCDC conversion circuit or an ACAC conversion circuit.
In an embodiment, the high thermal resistance path includes at least one insulating layer.
In the power conversion apparatus according to the present disclosure, the additional high heat capacity device is connected to the heating element via the low thermal resistance path, such that the heat capacity of the heating element 202 is increased. Therefore, in a case that the temperature of the heating element rises rapidly due to a large transient loss, the rate at which the temperature of the heating element rises is reduced, such that the temperature of the heating element at the end of the peak condition in a short period of time is lowered, thereby ensuring reliability of the power conversion apparatus. In addition, it is unnecessary to adopt a switch transistor with high performance or connect more switch transistors in parallel as in the conventional technology. Therefore, the size, the weight and costs of the system are reduced.
In order to more clearly describe the technical solutions in the embodiments of the present disclosure or the technical solutions in the conventional technology, drawings to be used in the description of the embodiments of the present disclosure or the conventional technology are briefly described hereinafter. It is apparent that the drawings described below illustrate merely some embodiments of the present disclosure, and those skilled in the art may obtain other drawings based on the structures shown in the drawings without any creative effort.
Technical solutions in the embodiments of the present disclosure are clearly and completely described below with reference to the drawings in the embodiments of the present disclosure. It is apparent that the embodiments described in the following are only some rather than all of the embodiments of the present disclosure. Any other embodiments obtained by those skilled in the art based on the embodiments in the present disclosure without any creative work fall within the protection scope of the present disclosure.
In the present disclosure, terms “include”. “comprise” or any other variants thereof are intended to be non-exclusive. Therefore, a process, method, article or device including a series of elements includes not only these elements but also elements that are not enumerated, or elements that are inherent to the process, method, article or device. Unless expressively limited otherwise, an element limited by “comprising/including a(n) . . . ” does not exclude existence of another identical element in the process, method, article or device including the element.
There is a problem that the system is large in size and weight, and has high costs existing in all of the above existing technical solutions such as adopting the switch transistor with high performance or connecting multiple switch transistors in parallel or adopting the heat dissipation device with high heat dissipation capacity. Therefore, a power conversion apparatus is provided according to the present disclosure, to solve the problem of large size, large weight and high costs of the system existing in the conventional technology.
It should be noted that this embodiment is described by an example in which the power conversion apparatus includes one heating element 202.
In practice, the low thermal resistance path 203 is made of one kind of metal or multiple kinds of metal, for example, a surface metal of the PCB (including an aluminum substrate) and solder for the surface metal. The surface metal of the PCB is generally made of copper foil. Since the copper is prone to oxidation in common environment, it is impossible to apply tin on the surface metal (of poor solderability). Therefore, the copper surface is protected by processes such as hot air solder leveling (HASL), electroless nickel immersion gold (ENIG), immersion silver, immersion tin, and organic solderability preservative (OSP). These processes are not limited herein. The chip lead frame 301 soldered with the heating element 202 is soldered to the copper foil printed on the PCB at the other side of the chip lead frame 301. In many application scenarios, since one apparatus generally includes various power device chips 302 to implement their respective functions, multiple heating elements 202, for example, a heating element 1 to a heating element 5 in
That is, the heating element 202 itself is small in size, and the low thermal resistance path 203 is also small in size, leading to a relatively low overall heat capacity of the system.
In addition, the high thermal resistance path 204 includes at least one insulating layer, which may actually be an insulating layer in the aluminum substrate and the heat conductive silicone grease and the like. It is well known that the insulating layer and the heat conductive silicone grease each have low thermal conductivity, even less than one percent of the metal for the chip lead frame 301, the PCB and the like. In addition, the insulating layer generally has a certain thickness in order to ensure insulation performance and processing performance (for example, anti-breakage or anti-cracking) of the insulating layer.
In a case that the heating element 202 of small heat capacity is arranged on the low thermal resistance path 203, and then the low thermal resistance path 203 is arranged on the heatsink 205 via the high thermal resistance path 204, the heating element 202 generates a large amount of heat in response to a large amount of power consumption in a short period of time. In this case, on the one hand the heat is transferred to the heatsink 205 through the high thermal resistance path 204, and on the other hand the heat is shared between the heating element 202 and the PCB. However, the overall heat capacity is small and the rate at which the heat is transferred to the heatsink 205 through the high thermal resistance path 204 is slow, inevitably resulting in a sharp rise in temperature of the heating element 202, thereby affecting the reliability of the apparatus.
In view of this, the additional high heat capacity device 201 is connected to the heating element 202 though the low thermal resistance path 203. The additional high heat capacity device 201 is large in size, leading to an increase in heat capacity of the heating element 202. Therefore, the rise in temperature of the heating element 202 is slowed down in a case that the power device chip 302 causes a large amount of power consumption in a short period of time.
Referring to
In addition, referring to
Only some examples of the additional high heat capacity device 201 are described above, and the present disclosure is not limited thereto. The additional high heat capacity device 201 in any shape that increasing the heat capacity of the heating element 202 is within the protection scope of the present disclosure. A copper strip or a copper block is soldered on the copper foil printed on the PCB and around the power component chip 302, such that the temperature at the peak is reduced.
Further, the operation principle of the additional high heat capacity device 201 is explained based on the following formula for heat energy and formula for thermal conduction.
The formula for thermal energy is expressed as q=cmΔT.
q represents absorbed or released thermal energy (J). c represents the specific heat capacity of the material (J/(kg·° C.)). m represents mass of the material (kg). ΔT represents a difference in temperature (° C.). It can be seen that in order to reduce the rate at which the temperature of an object rises in a case that absorbed heat energy is identical to the released heat energy, the specific heat capacity and the mass of the material that the object is made of are increased.
The formula for heat conduction is expressed as
Q represents the heat conduction flow (W). λ represents thermal conductivity (W/m·° C.) of the material. A represents the cross-sectional area (m2) perpendicular to the direction of heat transfer.
represents a temperature gradient (° C./m) along a normal line to the isothermal surface. The negative sign in the formula indicates that the direction of heat transfer is opposite to the temperature gradient. It can be seen that in order to increase the amount of heat dissipated through heat transfer, the thermal conductivity of the material is increased. For example, a material with high thermal conductivity (copper or aluminum) is selected. Alternatively, a cross-sectional area of the additional high heat capacity device 201 in the direction of heat transfer is increased.
In the power conversion apparatus according to the present disclosure, the additional high heat capacity device is connected to the heating element via the low thermal resistance path, such that the heat capacity of the heating element 202 is increased. Therefore, in a case that the temperature of the heating element rises rapidly due to a large transient loss, the rate at which the temperature of the heating element rises is reduced, such that the temperature of the heating element at the end of the peak condition in a short period of time is lowered, thereby ensuring the reliability of the power conversion apparatus. In addition, it is unnecessary to adopt a switch transistor with high performance or connect more switch transistors in parallel as in the conventional technology. Therefore, the size, the weight, and costs of the system are reduced.
Referring to
It should be noted that, there are following solutions in the conventional technology to the operation condition of large power consumption of the system due to the peak output in a short period of time. For example, a switch transistor with a high performance is adopted or multiple switch transistors are connected in parallel in the system to reduce the peak power consumption of the system, thereby reducing the rate at which the temperature of the heating component rises. Alternatively, a material with high thermal conductivity, such as an aluminum substrate and a heat conductive silicone grease is selected to accelerate the transfer of the heat generated by the heating element to the heatsink. Alternatively, a heat dissipation device with high heat dissipation capacity is arranged to reduce the temperature of the system itself.
It can be seen that in all the technical solutions existing in the conventional technology, a margin by which the temperature of the system rises in the rated condition is increased, so as to solve the problem that the temperature of the system rises rapidly due to a sharp rise in temperature of the heating element in order to meet the peak condition in a short period of time.
In addition, the above technical solutions have the same drawbacks. The adopting a switch transistor with high performance or connecting multiple switch transistors in parallel inevitably results in an increase in costs of the heating element itself. Further, connecting multiple switch transistors in parallel inevitably results in an increase in size of the PCB board. Selecting a material with high thermal conductivity or adopting a heat dissipation device with high heat dissipation capacity also results in high costs, and even results in an increase in the size and weight of the heat dissipation device. In summary, the system according to the above conventional solutions is large in size and weight, and has high costs.
In the power conversion apparatus according to the embodiments of the present disclosure, an additional high heat capacity device 201 is arranged on the low thermal resistance path 203, such that the heat capacity of the heating element 202 is increased, thereby increasing the ability of the heating element 202 to store heat at the peak condition without changing the rise in the temperature in the rated condition. In addition, no change is made to the heating element or the heat dissipation device, leading to no increase in the size or weight as well as the costs of the system.
The embodiments in this specification are described in a progressive manner, the same or similar parts among the embodiments may be referred to each other, and each of the embodiments emphasizes the differences between the embodiment and other embodiments. In particular, since the system or the embodiment of the system is similar to the embodiment of the method, the description of the system or the embodiment of the system is simple, and reference may be made to the relevant part of the embodiment of the method. The above-described system and the embodiment of the system is only illustrative. Units described as separated components may be physically separated or not. Components shown as units may be physical units or not, i.e. may be located in one place or may be distributed onto multiple network units. Some or all modules thereof may be selected as required to implement the solution in the embodiments. Those skilled in the art can understand and implement the embodiments without any creative work.
Those skilled in the art should further noted that, units and algorithm steps of examples described in conjunction with the embodiments disclosed herein may be implemented by electronic hardware, computer software or a combination thereof. In order to clearly illustrate interchangeability of the hardware and the software, steps and elements of each embodiment have been described generally in terms of functions in the above specification. Whether these functions are implemented in hardware or software depends on the specific application and design constraints for the technical solution. Those skilled in the art may implement the described functions for each particular application in various manners, and such implementation should not be regarded as going beyond the scope of the present disclosure.
The disclosed embodiments are disclosed above, so that those skilled in the art may implement or use technical solutions of the present disclosure. Those skilled in the art will easily think of various modifications to the embodiments, and general principles defined in the present disclosure may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is to be accorded the widest scope consistent with the principles and novel features disclosed herein rather than intended to be limited to the embodiments described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202020837107.2 | May 2020 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2021/094057 | 5/17/2021 | WO |
