Power supply resistance value detection type thermal inductance alarm circuit

Abstract

The utility model discloses a power supply resistance detection type thermal inductance alarm circuit, which comprises a power supply circuit, a control circuit, a temperature detection circuit and an alarm circuit, the power supply circuit comprises a power supply reverse connection prevention module and a resistance detection module, the output end of the power supply reverse connection prevention module is connected to the input end of the resistance detection module, the output end of the resistance detection module is connected to the first input end of the control circuit, and the control end of the resistance detection module is connected to the first output end of the control circuit; the output end of the reverse power connection prevention module supplies power to the power supply end of the control circuit, the PWM output end of the control circuit is connected to the power supply end of the temperature detection circuit, and the output end of the temperature detection circuit is connected to the second input end of the control circuit; the output end of the power reverse connection prevention module supplies power to the power supply end of the alarm circuit, and the control end of the alarm circuit is connected to the second output end of the control circuit. The power supply resistance value detection type thermal inductance alarm circuit solves the problem that the resistance value of a power supply circuit cannot be detected in the prior art.

Description

Technical Field

[0001] This utility model relates to the field of temperature alarm devices, specifically to a resistance-value detection type thermal alarm circuit. Background Technology

[0002] A thermal alarm is a temperature alarm that detects temperature and triggers an alarm when the temperature is too high.

[0003] Chinese patent discloses a methane temperature alarm with application number CN202323627069.0. The methane temperature alarm includes: an upper shell, a lower shell, a sensing and actuating component, and an alarm device. The upper shell and the lower shell are fastened together to form a chamber, and the sensing and actuating component and the alarm device are installed in the chamber. The sensing and actuating component includes: a start switch, a detection and control circuit, and a sensor device. The sensor device includes: a methane sensor and a temperature sensor. The methane sensor is used to detect ambient methane, and the temperature sensor is used to detect the temperature of the methane. The detection and control circuit is mounted on a circuit board and includes: an amplification module, an analog-to-digital converter chip U3, and a controller U1. The output terminal of the methane sensor is connected to the input terminal of the amplification module.

[0004] Although the above-mentioned methane temperature alarm can monitor temperature, it still has the following drawbacks: it cannot detect the resistance of the power supply circuit, which makes it impossible to know the current of the power supply circuit. This can easily lead to the current at the temperature sensing part being too small, thus affecting the detection results. Utility Model Content

[0005] This utility model provides a resistance-detection type thermal alarm circuit, solving the problem that existing technologies cannot detect the resistance value of the power supply circuit.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This utility model discloses a resistance-value detection type thermal alarm circuit, including: a power supply circuit, a control circuit, a temperature detection circuit, and an alarm circuit; the power supply circuit includes: a reverse power connection protection module and a resistance detection module. The input terminal of the reverse power connection protection module is connected to the power supply, the output terminal of the reverse power connection protection module is connected to the input terminal of the resistance detection module, the output terminal of the resistance detection module is connected to the first input terminal of the control circuit, and the control terminal of the resistance detection module is connected to the first output terminal of the control circuit; the output terminal of the reverse power connection protection module supplies power to the control circuit, the PWM output terminal of the control circuit is connected to the power supply terminal of the temperature detection circuit, and the output terminal of the temperature detection circuit is connected to the second input terminal of the control circuit; the output terminal of the reverse power connection protection module supplies power to the alarm circuit, and the control terminal of the alarm circuit is connected to the second output terminal of the control circuit.

[0008] Preferably, the resistance detection module includes: a constant load unit and a control-access load unit. The high-voltage terminal of the constant load unit is connected to the high-voltage terminal of the control-access load unit. The output terminal in the middle of the constant load unit is the output terminal of the resistance detection module. The high-voltage terminal of the control-access load unit is connected to the output terminal of the reverse power supply protection module. The low-voltage terminals of both the constant load unit and the control-access load unit are grounded. The control terminal of the control-access load unit is the control terminal of the resistance detection module.

[0009] Preferably, the control-access load unit includes: NPN transistor Q2, NPN transistor Q3, resistor R2, and resistor R3. The base of NPN transistor Q2 is connected to the first terminal of resistor R2 and the collector of NPN transistor Q3. The second terminal of resistor R2 is the control terminal of the control-access load unit. The collector of NPN transistor Q2 is the high-voltage terminal of the control-access load unit. The emitter of NPN transistor Q2 is connected to the first terminal of resistor R3. The second terminal of resistor R3 and the emitter of NPN transistor Q3 are connected to form the low-voltage terminal of the control-access load unit.

[0010] Preferably, the constant load unit includes a resistor R4 and a capacitor C3. The first end of the resistor R4 is the high-voltage end of the constant load unit, the second end of the resistor R4 is connected to the positive terminal of the capacitor C3, the negative terminal of the capacitor C3 is the low-voltage end of the constant load unit, and the positive terminal of the capacitor C3 is the output terminal of the resistance detection module.

[0011] Preferably, the reverse power connection protection module includes: a PMOS transistor Q1, a capacitor C1, and a resistor R1. The drain of the PMOS transistor Q1 is connected to the positive terminal of the capacitor C1. The positive terminal of the capacitor C1 is the input terminal of the reverse power connection protection module. The gate of the PMOS transistor Q1 is connected to the first terminal of the resistor R1. The second terminal of the resistor R1 and the negative terminal of the capacitor C1 are grounded. The source of the PMOS transistor Q1 is the output terminal of the reverse power connection protection module.

[0012] Preferably, the temperature detection circuit includes: a thermistor RT1, a resistor R5, and a capacitor C2. The first terminal of the thermistor RT1 is the power supply terminal of the temperature detection circuit, the second terminal of the thermistor RT1 is the output terminal of the temperature detection circuit, the second terminal of the thermistor RT1 is connected to the first terminal of the resistor R5 and the positive terminal of the capacitor C2, and the second terminal of the resistor R5 and the negative terminal of the capacitor C3 are grounded.

[0013] Preferably, the alarm circuit includes: a buzzer BZ1, an inductor L1, a diode D1, an NPN transistor Q4, and a resistor R6. The positive terminal of the buzzer BZ1 is the power supply terminal of the alarm circuit. The positive terminal of the buzzer BZ1 is connected to the first end of the coil in the inductor L1, and the negative terminal of the buzzer BZ1 is connected to the second end of the coil in the inductor L1. The middle part of the coil in the inductor L1 is connected to the cathode of the diode and the collector of the NPN transistor Q4. The anode of the diode and the emitter of the NPN transistor Q4 are grounded. The base of the NPN transistor Q4 is connected to the first end of the resistor R6, and the second end of the resistor R6 is the control terminal of the alarm circuit.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] In this application, a reverse power connection protection module is set up to limit the current direction and prevent damage to the control circuit and temperature detection circuit caused by reverse voltage connection. Then, a resistance detection module is set up to detect the resistance value of the line between the power supply output terminal and the output terminal of the reverse power connection protection module. This allows the reverse power connection protection module to be debugged before production so that the resistance value of the reverse power connection protection module meets the requirements. It also allows the detection of whether the reverse power connection protection module has been damaged under normal conditions and to detect whether the reverse power connection protection module is supplying power normally.

[0016] Other advantages, objectives and features of this invention will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of this invention. Attached Figure Description

[0017] Figure 1 This is a circuit diagram of the power supply circuit in a resistance-value detection type thermal alarm circuit.

[0018] Figure 2 This is a circuit diagram of the temperature detection circuit in a resistance-based thermal alarm circuit.

[0019] Figure 3 This is a circuit diagram of the alarm circuit in a resistance-based thermal alarm circuit. Detailed Implementation

[0020] To make the technical means, creative features, achieved objectives and functions of this utility model clearer and easier to understand, the utility model will be further described below with reference to the accompanying drawings and specific embodiments:

[0021] This utility model discloses a resistance-value detection type thermal alarm circuit, including: a power supply circuit, a control circuit, a temperature detection circuit, and an alarm circuit; the power supply circuit includes: a reverse power connection protection module and a resistance detection module, the input terminal of the reverse power connection protection module is connected to the power supply, the output terminal of the reverse power connection protection module is connected to the input terminal of the resistance detection module, the output terminal of the resistance detection module is connected to the first input terminal of the control circuit, and the control terminal of the resistance detection module is connected to the first output terminal R_T of the control circuit; the output terminal of the reverse power connection protection module supplies power to the control circuit, the PWM output terminal of the control circuit is connected to the power supply terminal of the temperature detection circuit, and the output terminal of the temperature detection circuit is connected to the second input terminal of the control circuit; the output terminal of the reverse power connection protection module supplies power to the alarm circuit, and the control terminal of the alarm circuit is connected to the second output terminal of the control circuit.

[0022] In this application, the control circuit uses a control chip with PWM pulse width modulation function. The control chip can be a CW32L010 model, or other models. After the voltage of the reverse power supply protection module is connected to the power supply terminal of the control circuit, the PWM output terminal of the control circuit has a voltage with a pulse width. The length of the pulse width controls the running time of the temperature detection circuit, enabling the temperature detection circuit to operate under the control of the control circuit.

[0023] The resistance detection module includes a constant load unit and a control-access load unit. The high-voltage terminal of the constant load unit is connected to the high-voltage terminal of the control-access load unit. The output terminal in the middle of the constant load unit is the output terminal of the resistance detection module. The high-voltage terminal of the control-access load unit is connected to the output terminal of the reverse power supply protection module. The low-voltage terminals of both the constant load unit and the control-access load unit are grounded. The control terminal of the control-access load unit is the control terminal of the resistance detection module.

[0024] In this application, the control-access load unit includes: NPN transistor Q2, NPN transistor Q3, resistor R2, and resistor R3. The base of NPN transistor Q2 is connected to the first terminal of resistor R2 and the collector of NPN transistor Q3. The second terminal of resistor R2 is the control terminal of the control-access load unit. The collector of NPN transistor Q2 is the high-voltage terminal of the control-access load unit. The emitter of NPN transistor Q2 is connected to the first terminal of resistor R3. The second terminal of resistor R3 and the emitter of NPN transistor Q3 are connected to form the low-voltage terminal of the control-access load unit.

[0025] Preferably, the constant load unit includes a resistor R4 and a capacitor C3. The first terminal of the resistor R4 is the high-voltage terminal of the constant load unit, the second terminal of the resistor R4 is connected to the positive terminal of the capacitor C3, the negative terminal of the capacitor C3 is the low-voltage terminal of the constant load unit, and the positive terminal of the capacitor C3 is the output terminal of the resistance detection module. The capacitor C3 serves as a voltage regulator.

[0026] The first input terminal VDD of the control circuit has a built-in load, and the second terminal of resistor R4 is grounded through the built-in load of the control circuit.

[0027] The principle for testing the resistance value at the reverse power connection protection module is as follows: First, the control-connected load unit is not connected under the control of the control circuit. At this time, the first output terminal R_T of the control circuit outputs a low level, and both NPN transistors Q2 and Q3 in the control-connected load unit are disconnected. Since resistor R3 is not connected, only resistor R4 and the built-in load of the control circuit are connected after the output terminal VCC of the reverse power connection protection module. The voltage value detected at the first input terminal VDD of the control circuit is VDD1. Knowing the resistance values ​​of resistor R4 and the built-in load of the control circuit, we can then determine... The voltage at the output terminal VCC of the reverse power connection protection module is VCC1. At this time, the reverse power connection protection module, resistor R4, and the built-in load of the control circuit are connected in series. Therefore, the current of the reverse power connection protection module is (VCC1-VDD1) / R4. Assuming the voltage provided by the external power supply is V01, the resistance at the reverse power connection protection module can be measured as (V01-VCC1)*R4 / (VCC1-VDD1). Then, the control access load unit is turned on under the control of the control circuit. At this time, the first output terminal R_T of the control circuit outputs a high level, and the N in the control access load unit is turned on. With both PN transistors Q2 and Q3 closed, and resistor R3 connected, the output terminal VCC of the reverse connection protection module is connected to resistors R3 and R4, along with the built-in load of the control circuit. The branch containing resistor R3 and the branch containing resistor R4 are connected in parallel. The total resistance of resistors R3, R4, and the built-in load of the control circuit is different from the resistance of resistor R4 and the built-in load of the control circuit. The voltage detected at the first input terminal VDD of the control circuit is VDD2. Since the resistance of resistor R4 and the built-in load of the control circuit is known... We know that the voltage at the output terminal VCC of the reverse power connection protection module is VCC2. At this time, the current of the reverse power connection protection module is equal to the sum of the currents in the branch where resistor R4 is located and the current in the branch where resistor R3 is located. Let the resistance between the collector and emitter of NPN transistor Q2 be R0. Therefore, the current of the reverse power connection protection module is: (VCC2-VDD1) / R4+VCC2 / (R3+R0). Let the voltage provided by the external power supply be V01. We get the resistance at the reverse power connection protection module as: V01 / [(VCC2-VDD1) / R4+VCC2 / (R3+R0)].

[0028] Although the resistance at the reverse power connection protection module can be measured without connecting the control-access load unit, calculating this resistance is very cumbersome in practical applications. Therefore, the control circuit in this application can control whether the control-access load unit is connected or not. If the resistance of the reverse power connection protection module is large, then VDD1 and VDD2 will differ significantly. Therefore, the detection value of VDD at the first input terminal of the control circuit can directly determine whether the resistance of the reverse power connection protection module is too large, thus determining whether the selected reverse power connection protection module is suitable.

[0029] In this application, the reverse power connection protection module includes: a PMOS transistor Q1, a capacitor C1, and a resistor R1. The drain of the PMOS transistor Q1 is connected to the positive terminal of the capacitor C1, which is the input terminal of the reverse power connection protection module. The gate of the PMOS transistor Q1 is connected to the first terminal of the resistor R1. The second terminal of the resistor R1 and the negative terminal of the capacitor C1 are grounded. The source of the PMOS transistor Q1 is the output terminal of the reverse power connection protection module. The PMOS transistor Q1 is a type with a body diode, with the anode of the body diode connected to the drain of the PMOS transistor Q1 and the cathode connected to the source of the PMOS transistor Q1. The PMOS transistor Q1 serves to limit the direction of current. The preferred PMOS transistor Q1 is the YJL2305A model with an almost zero resistance. The capacitor C1 and resistor R1 serve a voltage stabilizing function.

[0030] In this application, the temperature detection circuit includes a thermistor RT1, a resistor R5, and a capacitor C2. The first terminal of the thermistor RT1 is the power supply terminal of the temperature detection circuit, and the second terminal of the thermistor RT1 is the output terminal of the temperature detection circuit. The second terminal of the thermistor RT1 is connected to the first terminal of the resistor R5 and the positive terminal of the capacitor C2, while the second terminal of the resistor R5 and the negative terminal of the capacitor C2 are grounded. The thermistor RT1 senses temperature, and its resistance changes with temperature changes. Therefore, the voltage value at the second terminal of the thermistor RT1 also changes. The second input terminal of the control circuit determines the temperature change by detecting this change.

[0031] In this application, the alarm circuit includes: a buzzer BZ1, an inductor L1, a diode D1, an NPN transistor Q4, and a resistor R6. The positive terminal of the buzzer BZ1 is the power supply terminal of the alarm circuit. The positive terminal of the buzzer BZ1 is connected to the first end of the coil in inductor L1, and the negative terminal of the buzzer BZ1 is connected to the second end of the coil in inductor L1. The middle part of the coil in inductor L1 is connected to the cathode of the diode and the collector of the NPN transistor Q4. The anode of the diode and the emitter of the NPN transistor Q4 are grounded. The base of the NPN transistor Q4 is connected to the first end of the resistor R6, and the second end of the resistor R6 is the control terminal of the alarm circuit. The control circuit controls whether the buzzer BZ1 is energized by controlling the voltage at the base of the NPN transistor Q4, thereby realizing the alarm function when the temperature is too high by controlling the buzzer BZ1 to be energized.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this utility model without departing from the spirit and scope of the technical solutions of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A resistance-value detection type thermal alarm circuit, characterized in that, include: Power supply circuit, control circuit, temperature detection circuit, and alarm circuit; The power supply circuit includes: a reverse power connection protection module and a resistance detection module. The input terminal of the reverse power connection protection module is connected to the power supply, the output terminal of the reverse power connection protection module is connected to the input terminal of the resistance detection module, the output terminal of the resistance detection module is connected to the first input terminal of the control circuit, and the control terminal of the resistance detection module is connected to the first output terminal of the control circuit. The output of the reverse power supply protection module supplies power to the control circuit power supply terminal. The PWM output of the control circuit is connected to the power supply terminal of the temperature detection circuit, and the output of the temperature detection circuit is connected to the second input terminal of the control circuit. The output terminal of the reverse power supply protection module supplies power to the alarm circuit's power supply terminal, and the control terminal of the alarm circuit is connected to the second output terminal of the control circuit.

2. The resistance-value detection type thermal alarm circuit according to claim 1, characterized in that, The resistance detection module includes a constant load unit and a control-access load unit. The high-voltage terminal of the constant load unit is connected to the high-voltage terminal of the control-access load unit. The output terminal in the middle of the constant load unit is the output terminal of the resistance detection module. The high-voltage terminal of the control-access load unit is connected to the output terminal of the reverse power supply protection module. The low-voltage terminals of both the constant load unit and the control-access load unit are grounded. The control terminal of the control-access load unit is the control terminal of the resistance detection module.

3. The resistance-value detection type thermal alarm circuit according to claim 2, characterized in that, The control-access load unit includes: NPN transistor Q2, NPN transistor Q3, resistor R2, and resistor R3. The base of NPN transistor Q2 is connected to the first terminal of resistor R2 and the collector of NPN transistor Q3. The second terminal of resistor R2 is the control terminal of the control-access load unit. The collector of NPN transistor Q2 is the high-voltage terminal of the control-access load unit. The emitter of NPN transistor Q2 is connected to the first terminal of resistor R3. The second terminal of resistor R3 and the emitter of NPN transistor Q3 are connected to form the low-voltage terminal of the control-access load unit.

4. The resistance-value detection type thermal alarm circuit according to claim 3, characterized in that, The constant load unit includes a resistor R4 and a capacitor C3. The first end of the resistor R4 is the high-voltage end of the constant load unit, the second end of the resistor R4 is connected to the positive terminal of the capacitor C3, the negative terminal of the capacitor C3 is the low-voltage end of the constant load unit, and the positive terminal of the capacitor C3 is the output terminal of the resistance detection module.

5. The resistance-value detection type thermal alarm circuit according to any one of claims 1 to 4, characterized in that, The reverse power connection protection module includes: a PMOS transistor Q1, a capacitor C1, and a resistor R1. The drain of the PMOS transistor Q1 is connected to the positive terminal of the capacitor C1. The positive terminal of the capacitor C1 is the input terminal of the reverse power connection protection module. The gate of the PMOS transistor Q1 is connected to the first terminal of the resistor R1. The second terminal of the resistor R1 and the negative terminal of the capacitor C1 are grounded. The source of the PMOS transistor Q1 is the output terminal of the reverse power connection protection module.

6. The resistance-value detection type thermal alarm circuit according to claim 5, characterized in that, The temperature detection circuit includes: a thermistor RT1, a resistor R5, and a capacitor C2. The first terminal of the thermistor RT1 is the power supply terminal of the temperature detection circuit, and the second terminal of the thermistor RT1 is the output terminal of the temperature detection circuit. The second terminal of the thermistor RT1 is connected to the first terminal of the resistor R5 and the positive terminal of the capacitor C2, and the second terminal of the resistor R5 and the negative terminal of the capacitor C3 are grounded.

7. The resistance-value detection type thermal alarm circuit according to claim 6, characterized in that, The alarm circuit includes: a buzzer BZ1, an inductor L1, a diode D1, an NPN transistor Q4, and a resistor R6. The positive terminal of the buzzer BZ1 is the power supply terminal of the alarm circuit. The positive terminal of the buzzer BZ1 is connected to the first end of the coil in the inductor L1, and the negative terminal of the buzzer BZ1 is connected to the second end of the coil in the inductor L1. The middle part of the coil in the inductor L1 is connected to the cathode of the diode and the collector of the NPN transistor Q4. The anode of the diode and the emitter of the NPN transistor Q4 are grounded. The base of the NPN transistor Q4 is connected to the first end of the resistor R6, and the second end of the resistor R6 is the control terminal of the alarm circuit.

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