TWI452273B - Temperature detection circuit - Google Patents

Description

Temperature monitoring circuit

The invention relates to a temperature monitoring circuit.

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 will continue to rise. . When the temperature of the heating element has exceeded the temperature range of its normal operation, when the user continues to use the computer because it is undetectable, it is easy to reduce the service life of the heating element.

In view of the above, it is necessary to provide a temperature monitoring circuit to alert the user when the system temperature exceeds the set value.

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 connected to a power source through a first resistor, The two ends are grounded, the node between the negative temperature coefficient thermistor and the first resistor is connected to the cathode of the voltage regulator tube, and the cathode of the voltage regulator tube is directly connected to the first end of the prompting device, the voltage regulator tube The anode is connected to the cathode of the controllable crucible through a second resistor, and 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 sequentially passed through a third The resistor and a fourth resistor are grounded, and the control end of the controllable port is connected to a node between the third resistor and the fourth resistor.

The temperature monitoring circuit can alert the user through the prompting device when the system temperature exceeds the set value.

RT‧‧‧negative temperature coefficient thermistor

ZD‧‧‧ Zener

LED‧‧‧Light Emitting Diode

SCR‧‧‧Controlled

R1-R4‧‧‧ resistance

Vcc‧‧‧ power supply

F‧‧‧Fan

BZ‧‧‧ alarm

1 is a circuit diagram of a first preferred embodiment of a temperature monitoring circuit of the present invention.

2 is a circuit diagram of a second preferred embodiment of the temperature monitoring circuit of the present invention.

3 is a circuit diagram of a third preferred embodiment of the temperature monitoring circuit of the present invention.

Referring to FIG. 1, a preferred embodiment of the temperature monitoring circuit of the present invention includes a negative temperature coefficient thermistor RT, a Zener diode ZD, a light emitting diode LED, and a controllable SCR.

The first end of the thermistor RT is connected to a power source Vcc through a resistor R1, and the second end is grounded. The node between the thermistor RT and the resistor R1 is connected to the cathode of the Zener ZD, and the cathode of the Zener ZD is also directly connected to the anode of the LED, and the anode of the Zener ZD is transmitted through A 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 grounded through resistors R3 and R4 in sequence, and the control terminal of the controllable SCR is connected to the node between the resistors R3 and R4. Wherein, the node between the resistors R3 and R4 is denoted by A, the node between the anode of the Zener diode ZD and the resistor R2 is denoted as B, and the node between the cathode of the Zener diode ZD and the resistor R1 is denoted as C .

The working principle of the temperature monitoring circuit will be described below: according to the characteristics of the controllable 矽, the conduction condition 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 value of the node B. Recorded as VA>VB.

According to the circuit structure, the voltage value of node A is VA=VC×R4/(R4+R3), of node B. Voltage value VB=VC-VD, voltage value of node C VC=Vcc×RT/(R1+RT)=Vcc-Vcc×R1/(R1+RT), where VC is the voltage value of node C, and VD is voltage regulator The voltage values across the tube ZD, R1, R3, R4 and RT are the resistance values of the resistors R1, R3, R4 and RT, respectively. Therefore, the condition that the controllable SCR is turned on is: VC×R4/(R4+R3)>VC-VD, that is, VC<VD×(1+R1/R2).

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 R1-R4 satisfy the voltage of the node C VC=VD×(1+R1/R2): when the temperature is lower When the value is lower than the set value, the resistance value of the negative temperature coefficient thermistor RT is large, so that the voltage value VC at the node C becomes large, that is, VC>VD×(1+R1/R2). At this time, the controllable 矽SCR is not turned on, so that the illuminating diode LED does not emit light.

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, VC<VD×(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 high.

Of course, in other embodiments, the temperature monitoring circuit may further include a fan F, and the fan F is connected in parallel with the LED (as shown in FIG. 2). When the temperature is too high, the LED is illuminated. And the fan F starts working to lower the temperature of the system.

Referring to FIG. 3 together, in other embodiments, the LED 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.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. but The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims.

RT‧‧‧negative temperature coefficient thermistor

ZD‧‧‧ Zener

LED‧‧‧Light Emitting Diode

SCR‧‧‧Controlled

R1-R4‧‧‧ resistance

Vcc‧‧‧ power supply

Claims (7)

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 connected to a power source through a first resistor, The two ends are grounded, the node between the negative temperature coefficient thermistor and the first resistor is connected to the cathode of the voltage regulator tube, and the cathode of the voltage regulator tube is directly connected to the first end of the prompting device, the voltage regulator tube The anode is connected to the cathode of the controllable crucible through a second resistor, and 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 sequentially passed through a third The resistor and a fourth resistor are grounded, and the control end of the controllable port is connected to a node between the third resistor and the fourth resistor. 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. 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. A temperature monitoring circuit includes a negative temperature coefficient thermistor, a voltage regulator tube, a fan and a controllable cymbal, the first end of the negative temperature coefficient thermistor is connected to a power source through a first resistor, and the second The grounding end, 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 fan, the anode of the Zener tube Grounded through a second resistor, and directly connected to the cathode of the controllable crucible, 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 first The fourth resistor is grounded, and the control end of the controllable port is connected to the node between the third resistor and the fourth resistor. The temperature monitoring circuit of claim 4, further comprising a prompting device, the first end of the prompting device being connected to the first end of the fan, the second end of the prompting device and the second end of the fan Connected to the end. 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. 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.