US20110225982A1

US20110225982A1 - Cpu cooling circuit having thermoelectric element

Info

Publication number: US20110225982A1
Application number: US12/820,044
Authority: US
Inventors: Hai-Qing Zhou; Song-Lin Tong
Original assignee: Hongfujin Precision Industry Shenzhen Co Ltd; Hon Hai Precision Industry Co Ltd
Current assignee: Hongfujin Precision Industry Shenzhen Co Ltd; Hon Hai Precision Industry Co Ltd
Priority date: 2010-03-16
Filing date: 2010-06-21
Publication date: 2011-09-22
Also published as: CN102193604A; CN102193604B

Abstract

A CPU cooling circuit for a CPU includes a thermoelectric element and a current source circuit. The thermoelectric element includes a first thermoelectric substrate attached to the CPU, a second thermoelectric substrate opposite to the first thermoelectric substrate, a plurality of n-type semiconductor units and p-type semiconductor units alternately sandwiched between the first and the second thermoelectric substrates and electrically connected in series between a positive power supply input and a negative power supply input. The current source circuit is configured for providing driving current to flow through the n-type semiconductor units and the p-type semiconductor units of the thermoelectric element according to a temperature of the CPU.

Description

BACKGROUND

1. Technical Field
The present disclosure relates to a central processing unit (CPU) cooling circuit, and more particularly, to CPU cooling circuit having thermoelectric element.
2. Description of Related Art
During operation of an electronic element of an electronic device, such as a central processing unit (CPU) of a computer, a large amount of heat is often produced. The heat must be quickly removed from the CPU to prevent unstable operation or damage to the CPU. Typically, a heat sink made of aluminum or copper is attached to an outer surface of the CPU to absorb the heat from the CPU. The heat absorbed by the heat sink is then dissipated to the ambient air via a fan attached on the heat sink. However, dissipating heat to air is slow and inefficient. In addition, when the temperature of the CPU is high, the fan will keep operating at a high-speed of rotation, which wastes electric power and shortens the life of the fan.
Therefore, a new system is desired to overcome the above-described shortcomings.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of at least one embodiment. In the drawings, like reference numerals designate corresponding parts throughout the various views.

FIG. 1 is a diagram of a CPU cooling circuit having a thermoelectric element according to one embodiment of the present disclosure.

FIG. 2 is a side view of the thermoelectric element of the CPU cooling circuit in FIG. 1.

DETAILED DESCRIPTION

Reference will now be made to the drawings to describe various disclosed embodiments of the present disclosure in detail, wherein like numerals refer to like elements throughout.
Referring to FIGS. 1 to 2, a CPU cooling circuit 100 according to one embodiment of the present disclosure is shown. The CPU cooling circuit 100 includes a current source circuit 20 and a thermoelectric element 10 driven by the circuit 20. The circuit 20 controls a current output to the thermoelectric element 10 to cool a CPU (not shown) to which the thermoelectric element 10 is attached.
As shown in FIG. 2, the thermoelectric element 10 includes a first thermoelectric substrate 11 a coupled to the CPU and an opposite second thermoelectric substrate 11 b, a plurality of p-type semiconductor units 101 a, and a plurality of n-type semiconductor units 101 b. The thermoelectric element 10 further includes a first electrically conductive pattern 102 a and a second electrically conductive pattern 102 b formed at internal surfaces of the first and the second substrates 11 a and 11 b, respectively. Each of the n-type and the p- type semiconductor units 101 a and 101 b is sandwiched between the first and the second patterns 102 a and 102 b. The first and the second patterns 102 a and 102 b are connected to opposite ends of the semiconductor units 101 a and 101 b, respectively. In this embodiment, the semiconductor units 101 a and 101 b are alternately arranged to be electrically connected in series via the first and the second patterns 102 a and 102 b. In alternative embodiments, each adjacent pair of the semiconductor units 101 a and 101 b is electrically connected in parallel via the first and the second patterns 102 a and 102 b.
The thermoelectric element 10 further includes a positive power supply input 110 and an opposite negative power supply input 112 formed on the internal surface of the first substrate 11 a for receiving a driving current from the current source circuit 20.
When current flows through the semiconductor units 101 a and 101 b, pn junctions of the semiconductor units 101 a and 101 b attached to the first substrate 11 a have current flowing from the n-type semiconductor units 101 a to the p-type semiconductor units 101 b and form a cooler portion, whereas, other pn junctions of the semiconductor units 101 a and 101 b attached to the second substrate 11 b have current flowing from the p-type semiconductor units 101 b to the n-type semiconductor units 101 a and form a heater portion. Therefore, heat can be conducted from the first substrate 11 a to the opposite second substrate 11 b via the semiconductor units 101 a and 101 b. A heat conductive efficiency of the thermoelectric element 10 is in direct proportion to the current flowing therethrough.
The circuit 20 includes a voltage comparator 21, a thermal resistor R1, a current division resistor R2, a plurality of current sampling resistors R3, and a plurality of switches Q.
In this embodiment, the voltage comparator 21 is an LM358DRG4 chip produced by Texas Instruments, Incorporated. The voltage comparator 21 includes a first input I1, a second input I2, a third input I3, a fourth input I4, a first output O1, and a second output O2.
The thermal resistor R1 has a negative temperature index and its resistance decreases with an increase its temperature. In this embodiment, the thermal resistor R1 connects in parallel with the current division resistor R2 between the first input I1 and an external power supply VCC. In one embodiment, the thermal resistor R1 is positioned adjacent to the first substrate 11 a of the thermoelectric element 10 to sense a temperature of the thermoelectric element 10.
In this embodiment, as shown in FIG. 1, the plurality of switches Q includes five n-channel metal-oxide-semiconductor (NMOS) transistors. Each NMOS transistor Q includes a source electrode S, a drain electrode D, and a gate electrode S controlling an electrical conductivity between the source electrode S and the drain electrode D. The gate electrode G of each NMOS transistor Q connects to the first and the second outputs O1 and O2 of the voltage comparator 21. The drain electrode D of each NMOS transistor Q connects to the external power source VCC. The source electrode S of each NMOS transistor Q connects to the positive power supply input 110 of the thermoelectric element 10. The source electrode S of each NMOS transistor Q also connects to the second input I2 of the voltage comparator 21 via a resistor (not labeled). In alternative embodiments, the NMOS transistors Q can be replaced by some other kind of switch such as p-channel metal-oxide-semiconductor (PMOS) transistors, npn type bipolar transistors, or pnp type bipolar transistors.
In this embodiment, as shown in FIG. 1, the resistors R3 include five current sampling resistors R3 connected in parallel between the fourth input I4 of the voltage comparator 21 and ground. The fourth input I4 of the voltage comparator 21 also connects to the negative power supply input 112 of the thermoelectric element 10.
In operation, when a CPU attached to the first substrate 11 a of the thermoelectric element 10 normally works it can make the temperature of the thermoelectric element 10 increase, the resistance of the thermal resistor R1 correspondingly decreases according to the increased temperature of the thermoelectric element 10. Thus, a current flowing through the thermal resistor R1 is increased to improve an output power of the current source circuit 20 to drive the thermoelectric element 10 for cooling the CPU. The voltage comparator 21 also increases a driving voltage to gate electrode G of each NMOS transistor Q to increase a current flowing through the thermoelectric element 10.
The fourth input I4 is used to detect the current flowing through the thermoelectric element 10 and compares the current flowing through the thermoelectric element 10 with a reference voltage Vref of the third input I3. In one embodiment, when the current flowing through the thermoelectric element 10 is over 20 amperes, the voltage comparator 21 control the first output I1 to turn off the switches Q for protecting the circuit 20 and send an alarm signal to an external device, such as a speaker, to warn of the over-current condition of the CPU cooling circuit 100.
It is to be understood, however, that even though numerous characteristics and advantages of certain inventive embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only; and that changes may be made in detail, especially in matters of arrangement of parts within the principles of present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A CPU cooling circuit for a CPU, comprising:

a thermoelectric element comprising a first thermoelectric substrate attached to the CPU, a second thermoelectric substrate opposite to the first thermoelectric substrate, a plurality of n-type semiconductor units and p-type semiconductor units alternately sandwiched between the first and the second thermoelectric substrates and electrically connected in series between a positive power supply input and a negative power supply input; and

a current source circuit configured for providing driving current to flow through the n-type semiconductor units and the p-type semiconductor units of the thermoelectric element according to a temperature of the CPU.

2. The CPU cooling circuit of claim 1, wherein pn junctions of the p-type and the n-type semiconductor units attached to the first thermoelectric substrate have current flowing from the n-type semiconductor units to the p-type semiconductor units.

3. The CPU cooling circuit of claim 2, wherein pn junctions of the p-type and the n-type semiconductor units attached to the second thermoelectric substrate have current flowing from the p-type semiconductor units to the n-type semiconductor units.

4. The CPU cooling circuit of claim 1, wherein a heat conductive efficiency of the thermoelectric element is in direct proportion to the current flowing through the p-type and the n-type semiconductor units.

5. The CPU cooling circuit of claim 1, further comprising a first electrically conductive pattern and a second electrically conductive pattern formed at internal surfaces of the first and the second thermoelectric substrates, respectively, the p-type semiconductor units and the n-type semiconductor units are electrically connected via the first conductive pattern and the second conductive pattern.

6. The CPU cooling circuit of claim 1, wherein the current source circuit comprises a voltage comparator, a thermal resistor, a plurality of switches, and a plurality of current sampling resistors, the voltage comparator comprises a first input configured for receiving an external power supply via the thermal resistor, and a first output configured for controlling the current provided from the external power supply to the positive power supply input via the plurality of switches, the negative power supply input is grounded via the current sampling resistors.

7. The CPU cooling circuit of claim 6, wherein the plurality of switches are n-channel metal-oxide-semiconductor (NMOS) transistors.

8. The CPU cooling circuit of claim 7, wherein the first output connected to a gate electrode of each NMOS transistor, the external power supply is connected to the positive power supply input via a drain electrode and a source electrode of each NMOS transistor.

9. The CPU cooling circuit of claim 8, wherein the voltage comparator further comprises a second input connected to source electrode of each NMOS transistor via a resistor.

10. The CPU cooling circuit of claim 6, wherein the plurality of switches are p-channel metal-oxide-semiconductor (PMOS) transistors.

11. The CPU cooling circuit of claim 6, wherein the plurality of switches are npn type bipolar transistors.

12. The CPU cooling circuit of claim 6, wherein the plurality of switches are pnp type bipolar transistors.

13. The CPU cooling circuit of claim 6, wherein the voltage comparator further comprises a third input configured for receiving a reference voltage and a fourth input connected to the negative power input terminal to detect the current flowing through the thermoelectric element by the current sampling resistors.

14. The CPU cooling circuit of claim 6, wherein the thermal resistor has a negative temperature index.

15. The CPU cooling circuit of claim 14, wherein further comprising a current division resistor connected in parallel with the thermal resistor.