Heat dissipation device

A heat dissipation device positioned in a computer case, includes a fan, a plate positioned between the computer case and the fan, at least one motor contiguous with the fan, a motor driver, a fan driver, at least one temperature sensor sensing the temperature in the computer case, and a controller. The fan defines an air outlet facing the computer case. The plate is slidable relative to the air outlet to open or close the air outlet. The motor is configured for moving the plate. The motor driver is configured for driving the motor to work. The fan driver is configured for driving the fan to rotate. When the sensed temperature is higher than a preset threshold temperature, the controller controls the motor to move the plate from the air outlet, and controls the fan to rotate.

BACKGROUND

1. Technical Field

The present disclosure relates to a heat dissipation device and, particularly, to a heat dissipation device for a host computer.

2. Description of Related Art

Fans are often mounted on central processing units, power units, and video cards of computers to cool these units. Conventionally the cases of the computers have slots or holes to vent heated air from the computers to facilitate heat dissipation. However, as the development of computer performance increases, more powerful components are generating more heat. The slots are insufficient to timely and efficiently dissipate the heat.

What is needed, therefore, is a heat dissipation device to overcome the above-described problem.

DETAILED DESCRIPTION

Embodiments of the present disclosure will now be described in detail below, with reference to the accompanying drawings.

Referring toFIGS. 1 and 2, a host computer100according to one embodiment, is shown. The host computer100includes a housing10, a heat dissipation device20, and a circuit board30. The heat dissipation device20and the circuit board30are fixed in the housing10. In the present embodiment, the circuit board30is a motherboard.

An opening120is defined in a sidewall110of the housing10. Two substantially parallel sliding tracks130are fixed on the inner surface of the sidewall110corresponding to two opposite sides of the opening120.

The heat dissipation device20includes a controlling module200and a heat dissipation module300. The controlling module200is fixed on the circuit board30. The heat dissipation module30is fixed on the housing10.

The heat dissipation module300includes a fan310, a plate320, a first motor330, and a second motor340. The fan310includes a fan holder311defining an air outlet312facing the opening120. The fan310is fixed on the inner side of the housing10by the fan holder311.

The plate320is positioned between the fan holder311and the sidewall110for covering the air outlet312. Two opposite edges of the plate320are movably received in the sliding tracks130. A rack gear321is fixed on the plate320. The first motor330and the second motor340are fixed on opposite sides of the fan310. In the present embodiment, the first motor330and the second motor340are two-phase stepper motors. A first gear331and a second gear341are mounted on the first motor330and the second motor340respectively. Both the first gear331and the second gear341mesh with the rack gear321to drive the plate320along the sliding tracks130.

Referring toFIGS. 3 and 4, when the first motor330pulls the plate320and the second motor340pushes the plate320to drive the plate320along the sliding tracks130, the air outlet312is opened and communicates with the opening120. When the first motor330pushes the plate320and the second motor340pulls the plate320, the air outlet312is covered again by the plate320and isolated from the opening120. In an alternative embodiment, only one of the first motor330and the second motor340is employed if the employed motor is capable of efficiently driving the plate320along the sliding tracks130.

Referring toFIGS. 1 and 5, the controlling module200includes two temperature sensing circuits210, a main controller220, a fan driver240, and a motor driving circuit250. The temperature sensing circuits210, the fan driver240, and the motor driving circuit250are all electrically connected to the main controller220.

The temperature sensing circuits210are provided to sense the temperature inside the host computer100. Each temperature sensing circuit210includes a constant current source211, a first capacitor212, a temperature sensor213, a second capacitor214, an isolation amplifier215, an amplifier216, and a current limiting resistor217. In the present embodiment, the constant current source211, the first capacitor212, the temperature sensor213, the second capacitor214, the isolation amplifier215, the amplifier216, and the current limiting resistor217are installed on the circuit board30. The two temperature sensors213are installed on the inner surface of the sidewall110. The two temperature sensors213are positioned contiguous to each other to sense the temperature of substantially the same area, in case one should fail. The two temperature sensors213are connected in parallel to the main controller220.

A first terminal213aof the temperature sensor213is electrically connected to the constant current source211, and another terminal213bof the temperature sensor213is grounded. The first terminal213aof the temperature sensor213is also electrically connected to the non-inverting input of the isolation amplifier215by the current limiting resistor217. The current limiting resistor217is provided for limiting the current to the isolation amplifier215and further filtering noise from the current. The output of the isolation amplifier215is electrically connected to the inverting input of the amplifier216. The output of the amplifier216is electrically connected to the main controller220. An end of the first capacitor212is electrically connected between the first terminal213aof the temperature sensor213and the constant current source211, and an opposite end of the first capacitor212is grounded. The first capacitor212is provided for filtering noise from the current to improve the precision of the temperature sensor213. An end of the second capacitor214is electrically connected between the output of the current limiting resistor217and the non-inverting input of the isolation amplifier215, an opposite end of the second capacitor214is grounded.

The temperature sensors213are NTSD1XM202FPB30 thermistors. The temperature sensors213are provided for detecting the temperature inside the housing10. In an alternative embodiment, the host computer100can also use one or more than two temperature sensors213.

The constant current sources211are provided for supplying a corresponding stable power to the two temperature sensors213. In the present embodiment, the constant current sources211are LM334 feedback constant current sources.

The amplifiers216are configured for amplifying the signals from the temperature sensors213. The isolation amplifiers215are configured for increasing the power of the signal from the temperature sensors213.

In the present embodiment, the main controller220is installed on the circuit board30. The main controller220is a PIC16C73 chip. The main controller220includes two input terminals RA0/AN0and RA1/AN1, a fan controlling output terminal RC2, two first motor controlling output terminals RB7and RB6, and two second motor controlling output terminals RB5and RB4. The input terminals RA0/AN0and RA1/AN1are respectively electrically connected to a corresponding temperature sensing circuit210.

The motor driving circuit250is electrically connected to the first motor330and the second motor340and includes a motor driver251, four pull-up resistors252,253,254and255, and a voltage stabilizing circuit256. The motor driver251is electrically connected to the first and second motors330,340for driving the first motor330and the second motor340. The pull-up resistors252,253,254and255are connected in parallel between the main controller220and the motor driver251for increasing the driving capacity of the motor driver220. The voltage stabilizing circuit256is electrically connected to the first and second motors330,340for preventing the circuit board30from resetting when the first motor330and the second motor340are started. In the present embodiment, the motor driver251simultaneously drives the first motor330and the second motor340to rotate in opposite directions. The motor driver251is installed on the circuit board30. The motor driver251is a ULN2003 chip.

The motor driver251includes six inputs1-6and six outputs11-16. The inputs1and2are electrically connected together to form a first common input, the first common input is electrically connected to both the output terminal RB7of the main controller220and the pull-up resistor252. The input3is electrically connected to both the output terminal RB6and the pull-up resistor253. The outputs16and15are both electrically connected to one pole330aof the first motor330. The output14is electrically connected to the other pole330bof the first motor330.

The inputs4and5of the motor driver251are electrically connected together to form a second common input, the second common input is electrically connected to both the output terminal RB5of the main controller220and the pull-up resistor254. The input6of the motor driver251is electrically connected to both the output terminal RB4and the pull-up resistor255. The inputs1and2of the motor driver251are electrically connected together and the inputs4and5of the motor driver251are electrically connected together for increasing the driving capacity of the motor driver220. The outputs13and12of the motor driver251are both electrically connected to one pole340aof the second motor340. The output11of the motor driver251is electrically connected to the other pole340bof the second motor340.

The outputs15and16of the motor driver251are electrically connected together to the first motor330and the outputs12and13of the motor driver251are electrically connected together for increasing the driving capacity of the motor driver220.

The first motor330and the second motor340are supplied by a power supply P of the circuit board30. The voltage stabilizing circuit256is provided between the power supply P and the first and second motors330,340. The voltage stabilizing circuit256includes four capacitors256a,256b,256c, and256dconnected in parallel between the power supply P and the first motor330.

The fan driver240is provided for driving the fan310. In the present embodiment, the fan driver240is installed on the circuit board30. The fan driver240includes a fan driver input241and a fan driver output242. The input241is electrically connected to the output RC2of the main controller220. The output242is electrically connected to the fan310.

In the present embodiment, a first threshold temperature value and a second threshold temperature value lower than the first threshold temperature value are pre-stored in the main controller220. When the main controller220receives signals from the temperature sensors213, the main controller220converts the signals to digital values and compares the digital values with the first threshold temperature value and the second threshold temperature value. When the digital values are higher than the first threshold temperature value, the output terminals RB4, RB5, RB6, and RB7each output a first controlling signal to the motor driving circuit250. The output terminal RC2outputs a second controlling signal to the fan driver240. The motor driver251receives the first controlling signal from the output terminals RB4, RB5, RB6, and RB7, the motor driver251drives the first motor330to pull the plate320, and drives the second motor340to push the plate320.

When the digital values are lower than the second threshold temperature value and the fan is running, the output terminals RB4, RB5, RB6, and RB7each output a third controlling signal to the motor driving circuit250. The output terminal RC2outputs a fourth controlling signal to the fan driver240. The running of the fan310can be detected by the main controller220according to the state of a variable. In the present embodiment, a variable is pre-stored and updated in the main controller220. The variable can be changed between “0” and “1.” The variable is initially set to “0” and changed to “1” by the main controller220when the output terminal RC2outputs a second controlling signal to the fan driver240. The variable is changed back to “0” when the output terminal RC2outputs a fourth controlling signal to the fan driver240. When the digital values are lower than the second threshold temperature value and the variable is “1”, the main controller310outputs a third controlling signal to the motor driving circuit250and outputs a fourth controlling signal to the fan driver240. When the motor driver251receives the third controlling signal from the output terminals RB4, RB5, RB6, and RB7, the motor driver251drives the first motor330to push the plate320, and drives the second motor340to pull the plate320.

In an alternative embodiment, only one threshold temperature value may be pre-stored in the main controller220. When the digital values are higher than the threshold temperature value, the main controller220controls the motor driving circuit250and the fan driver240to activate the fan310and move the plate320to uncover the opening120. The main controller220is electrically connected to a CPU (not shown) of the host computer100. The main controller220controls the fan310to stop and the plate320is moved to cover the opening120again until the host computer100receives a power off signal from the CPU, and the main controller220sends a feedback signal to the CPU to power off the host computer100after the plate320covers the opening120.

In the present embodiment, the main controller220is programmed to firstly output the first controlling signal to the motor driving circuit250, and after a delay, such as about one second, output the second controlling signal to the fan driver240. When the digital values are higher than the first threshold temperature value, the opening120is opened before the fan300begins operating. The main controller220is programmed to firstly output the fourth controlling signal to the fan driver240, and after a delay, such as about one second, output the third controlling signal to the motor driving circuit250. When the digital values are lower than the second threshold temperature value, the opening120is closed after the fan300stops.

In the present embodiment, the main controller220is pre-programmed to control the number of rotation steps of the first motor330and the second motor340each time the plate320is moved to open or close the opening120, so as to stop the plate320at the preset position. In an alternative embodiment, position switches (not shown) are provided for signaling the main controller220to stop the plate320at preset positions.

While certain embodiments have been described and exemplified above, various other embodiments will be apparent to those skilled in the art from the foregoing disclosure. The present disclosure is not limited to the particular embodiments described and exemplified, and the embodiments are capable of considerable variation and modification without departure from the scope of the appended claims.