TW201229472A - Temperature detection circuit - Google Patents

Abstract

A temperature detection circuit includes a Negative Temperature Coefficient (NTC) resistor, a zener diode, an alarm, and a thyristor. A first terminal of the NTC resistor is connected to a power supply through a first resistor. A second terminal of the NTC resistor is grounded. A node between the NTC resistor and the first resistor is connected to a cathode of the thyristor. The cathode of the thyristor is connected to a first terminal of the alarm. An anode of the thyristor is grounded through a second resistor. The anode of the thyristor is connected to a second terminal of the alarm. The first terminal of the alarm is grounded through a third resistor and a fourth resistor in series. A control terminal of the thyristor is connected to a node between the third resistor and the fourth resistor.

Description

201229472 VI. Description of the Invention: [Technical Field of the Invention] [0001] The present invention relates to a temperature monitoring circuit. [Prior Art] [0002] When the computer is working, the heating element on the motherboard (such as the central processing unit, etc.) will generate a large amount of heat. If the heat generated by the heating element cannot be removed by the heat sink installed on it, The temperature of the heating element continues to rise. When the temperature of the heating element has exceeded the normal operating temperature range, the user can easily reduce the service life of the heating element when the user continues to use the computer because it is undetectable. SUMMARY OF THE INVENTION [0003] In view of the above, it is necessary to provide a temperature monitoring circuit to alert a user when the system temperature exceeds a set value. [0004] A temperature monitoring circuit includes a negative temperature coefficient thermistor, a voltage stabilizing tube, a prompting device, and a controllable cymbal, the first end of the negative temperature coefficient thermistor is transmitted through a first resistor and a power source Connected, the second end is grounded, the node between the negative temperature coefficient thermistor and the first resistor is connected to the cathode of the Zener tube, and the cathode of the Zener tube is also directly connected to the first end of the prompting device, The anode of the Zener tube is grounded through a second resistor, and is also directly connected to the cathode of the controllable crucible. The anode of the controllable crucible is connected to the second end of the prompting device, and the first end of the prompting device is also sequentially transmitted through A third resistor and a fourth resistor are grounded, and the control terminal of the controllable port is connected to a node between the third resistor and the fourth resistor. [0005] The temperature monitoring circuit can alert the user through the prompting device when the system temperature exceeds the set value. 100100441 Form No. A0101 Page 4 / Total 12 Page 1002000750-0 201229472 [Embodiment] [0006] Referring to FIG. 1, a preferred embodiment of the temperature monitoring circuit of the present invention includes a negative temperature coefficient thermistor RT, a voltage regulator Tube ZD, a light-emitting diode led and a controllable SCR. [0007] The first end of the thermistor RT is connected to a power source Vcc through a resistor μ, and the second terminal is grounded. The node between the thermistor RT and the resistor R1 is connected to the cathode of the Zener diode ZD, and the cathode of the Zener diode is also directly connected to the anode of the LED, and the anode of the Zener ZD is transmitted through - Resistor R2 is grounded and is also directly connected to the cathode of the controllable SCR. The anode of the controllable SCR is connected to the cathode of the LED. The anode of the LED is also connected through the resistors R3 and R4 in sequence, and the node of the controllable ♦ sc R and the resistors R3 and R4 are connected: wherein: between the resistors 3 and R4 The node is denoted by A, and the node between the anode of the Zener ZD and the resistor R2 is denoted as B'. The node between the cathode of the Zener z D and the resistor r 1 is denoted as C 〇 [0008] The principle of the temperature monitoring circuit is described as follows: Ο [0009] According to the characteristics of the controllable stone, the condition of its conduction is that the voltage value of the control terminal is higher than the voltage value of the cathode, that is, the voltage value of the node A is higher than the voltage of the node B. Value, recorded as VA > VB. [0010] 100100441

According to the circuit structure, the voltage value of node A is VA=VCxR4/(R4+R3) 'The voltage value of node B is VB = VC-VD, the voltage value of node C is VC = Vccx RT/(Rl + RT)=Vcc-VccxRl /(RHRT), where VC is node C

The voltage value, VD is the voltage value across the Zener ZD, and Ri, R3, R4 and RT are the resistance values of the resistors R1, R3, R4 and RT, respectively. Therefore, the condition of the controllable SCR SCR is: VCxR4/(R4 + R3)>VC-VD, that is, VCCVDx (Form No. A0101 Page 5 of 12 丨(10) 201229472 1+R1/R2). [0011] It is assumed that when the temperature is a certain set value, the resistance value of the negative temperature coefficient thermistor RT and the resistance of the resistor Rl-R4 satisfy the voltage of the node C VC = VDx (1+R1/R2): [0012] When the temperature is lower, that is, lower than the set value, the resistance value of the negative temperature coefficient thermistor RT is large, thereby causing the voltage value VC at the node C to become large, that is, making VC>VDx (1+R1/ R2). At this time, the controllable SCR is not turned on, so that the LED is not illuminated. [0013] When the temperature is higher, that is, greater than the set value, the resistance value of the negative temperature coefficient thermistor RT becomes small, thereby causing the voltage value VC at the node C to become small, that is, making VC<VDx (1+R1) /R2). At this time, the controllable SCR is turned on, so that the LED is illuminated to remind the user that the temperature is too south. [0014] Of course, in other embodiments, the temperature monitoring circuit may further include a fan F, the fan F is connected in parallel with the LED (as shown in FIG. 2), when the temperature is too high, the LED The body LED illuminates and the fan F begins to operate to reduce the temperature of the system. [0015] Please refer to FIG. 3 together. In other embodiments, the LEDs can also be other prompting devices, such as an alarm BZ. When the temperature is too high, the alarm BZ starts to work to remind the user. [0016] In summary, the present invention complies with the requirements of the invention patent, and submits a patent application according to law. However, the above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art of the present invention should be included in the following claims. 100100441 Form No. A0101 Page 6 of 12 1002000750-0 201229472 [Simple description]

1 is a circuit diagram of a first preferred embodiment of a temperature monitoring circuit of the present invention. [0018] FIG. 2 is a circuit diagram of a second preferred embodiment of the temperature monitoring circuit of the present invention. [0019] FIG. Circuit diagram of a third preferred embodiment of the temperature monitoring circuit [0020] [Description of main component symbols] Negative temperature coefficient thermistor: RT [0021] Zener: ZD [0022] LED: LED [0023] Controllable 矽: SCR [0024] Resistor: R1-R4 [0025] Power: Vcc CJ Just Fan: F [0027] Alarm: BZ 100100441 Form No. A0101 Page 7 / Total 12 Page 1002000750-0

Claims (1)

201229472 VII. Patent application scope: 1. A temperature monitoring circuit, comprising a negative temperature coefficient thermistor, a voltage regulator tube, a prompting device and a controllable 矽, the first end of the negative temperature coefficient thermistor is transmitted through a The first resistor is connected to a power source, the second end is grounded, the node between the negative temperature coefficient thermistor and the first resistor is connected to the cathode of the Zener tube, and the cathode of the Zener tube is also directly connected to the prompting device The first end is connected, the anode of the Zener tube is grounded through a second resistor, and is directly connected to the cathode of the controllable crucible. The anode of the controllable crucible is connected to the second end of the prompting device. One end is also grounded through a third resistor and a fourth resistor, and the control end of the controllable port is connected to a node between the third resistor and the fourth resistor. 2. The temperature monitoring circuit of claim 1, wherein the prompting device is a light emitting diode, the anode is a first end of the prompting device, and the cathode is a second end of the prompting device. 3. The temperature monitoring circuit of claim 1, wherein the prompting device is an alarm, the first end of which is a first end of the prompting device, and the second end is a second end of the prompting device. 4 . A temperature monitoring circuit comprising a negative temperature coefficient thermistor, a voltage regulator tube, a fan and a controllable 矽, the first end of the negative temperature coefficient thermistor is connected to a power source through a first resistor, The second end is grounded, the node between the negative temperature coefficient thermistor and the first resistor is connected to the cathode of the Zener tube, and the cathode of the Zener tube is directly connected to the first end of the fan, the Zener tube The anode is connected to the cathode of the controllable crucible through a second resistor. The anode of the controllable crucible is connected to the second end of the fan, and the first end of the fan is sequentially transmitted through a third resistor and A fourth resistor is grounded, and the controllable 100100441 form number A0101 1002000750-0 201229472 is connected to a node between the third resistor and the fourth resistor. 5. The temperature monitoring circuit of claim 4, further comprising a prompting device, the first end of the prompting device being coupled to the first end of the fan, the second end of the prompting device and the second end of the fan Connected. 6. The temperature monitoring circuit of claim 5, wherein the prompting device is a light emitting diode, the anode is a first end of the prompting device, and the cathode is a second end of the prompting device. 7. The temperature monitoring circuit of claim 5, wherein the prompting device is an alarm, the first end of which is a first end of the prompting device, and the second end is a second end of the prompting device. 1002000750-0 100100441 Form No. A0101 Page 9 of 12