Over-temperature protection switch circuit

Abstract

The utility model relates to an over-temperature protection switch circuit, which comprises a voltage reference circuit, an operational amplifier, a voltage division circuit and an MOS (Metal Oxide Semiconductor) tube, the voltage division circuit comprises an NTC resistor, a first resistor and a second resistor which are sequentially connected in series; the reverse input end of the operational amplifier detects a voltage division circuit composed of the NTC resistor, the first resistor and the second resistor; when the temperature rises, the voltage of the reverse input end of the operational amplifier gradually rises, and when the temperature reaches the set temperature of the third resistor and the fourth resistor, low level is output, and the MOS tube is closed, so that the DCDC output voltage is controlled to be closed to protect a post-stage circuit; when the temperature is reduced, the voltage of the reverse input end of the operational amplifier is gradually reduced, and when the temperatures set by the third resistor and the fourth resistor are reached, high level is output, and the MOS tube is started, so that the DCDC output voltage is controlled to be started for normal work; the circuit structure is simple, the hysteresis characteristic is achieved, meanwhile, temperature range configuration can be rapidly completed, and operation is simple.

Description

Technical Field

[0001] The utility model relates to the technical field of over-temperature protection circuits, and more specifically, to an over-temperature protection switch circuit. Background Art

[0002] The over-temperature protection circuit is a very important part of electronic devices. Its function is to automatically cut off the power supply or reduce the power when the device overheats, so as to prevent the device from being damaged or causing safety accidents. With the progress of technology, electronic devices are becoming more and more miniaturized and integrated, which leads to an increase in power density per unit volume, and further makes the device easier to heat up; the close arrangement of internal components of the device also makes it difficult for heat to dissipate quickly. Therefore, over-temperature protection has become one of the essential functions; for the existing over-temperature protection circuit with hysteresis characteristics, the circuit structure design is often too complex, and it is also difficult to quickly configure the temperature range adjustment. To solve this problem, an over-temperature protection switch circuit is needed. Summary of the Utility Model

[0003] The technical problem to be solved by the utility model is to provide an over-temperature protection switch circuit in view of the above-mentioned defects of the prior art.

[0004] The technical solution adopted by the utility model to solve its technical problems is as follows:

[0005] Construct an over-temperature protection switch circuit, which includes a voltage reference circuit, an operational amplifier, a voltage dividing circuit and a MOS transistor; the voltage reference circuit is used to provide a reference voltage for the operational amplifier; the MOS transistor is used to control the output state of the power supply; the voltage dividing circuit includes an NTC resistor, a first resistor and a second resistor connected in series in sequence; one end of the NTC resistor far away from the first resistor is connected to the working power supply input terminal, and one end of the second resistor far away from the first resistor is grounded; one end of the first resistor far away from the NTC resistor is connected to the negative input terminal of the operational amplifier; the positive input terminal of the operational amplifier is connected with a third resistor and a fourth resistor in parallel, one end of the third resistor far away from the positive input terminal of the operational amplifier is connected to the voltage reference circuit, and one end of the fourth resistor far away from the positive input terminal of the operational amplifier is connected to the output terminal of the operational amplifier; the positive power supply input terminal of the operational amplifier is connected to the working power supply input terminal, the negative power supply input terminal of the operational amplifier is grounded, and the output terminal of the operational amplifier is connected to the MOS transistor.

[0006] For the over-temperature protection switch circuit described in the present utility model, the voltage reference circuit includes a voltage reference IC, a fifth resistor, a sixth resistor, a seventh resistor, and a capacitor; the power supply pin of the voltage reference IC is electrically connected to the fifth resistor, and the other end of the fifth resistor is connected to the working power supply input terminal; the ground pin of the voltage reference IC is grounded; the output pin of the voltage reference IC is connected to the parallel-connected sixth resistor and seventh resistor, the other end of the sixth resistor is electrically connected to the power supply pin of the voltage reference IC and one end of the capacitor, the other end of the seventh resistor is electrically connected to the ground pin of the voltage reference IC and the other end of the capacitor; the other end of the sixth resistor is electrically connected to the third resistor.

[0007] For the over-temperature protection switch circuit described in the present utility model, the positive input terminal of the operational amplifier is connected to the parallel-connected eighth resistor and ninth resistor; the other end of the eighth resistor is connected to the working power supply input terminal, and the other end of the ninth resistor is grounded.

[0008] For the over-temperature protection switch circuit described in the present utility model, the MOS transistor is an N-channel MOS transistor, the G pole of the MOS transistor is connected to the output terminal of the operational amplifier, the S pole of the MOS transistor is connected to the DCDC power supply output terminal, the D pole of the MOS transistor is connected to the tenth resistor, and the other end of the tenth resistor is connected to the working power supply input terminal.

[0009] The beneficial effects of the present utility model are as follows: The reverse input terminal of the operational amplifier detects the voltage-dividing circuit composed of the NTC resistor, the first resistor, and the second resistor; when the temperature rises, the voltage at the reverse input terminal of the operational amplifier gradually increases, and when it reaches the temperature set by the third resistor and the fourth resistor, a low level is output to turn off the MOS transistor, thereby controlling the shutdown of the DCDC output voltage to protect the subsequent circuit; when the temperature drops, the voltage at the reverse input terminal of the operational amplifier gradually decreases, and when it reaches the temperature set by the third resistor and the fourth resistor, a high level is output to turn on the MOS transistor, thereby controlling the opening of the DCDC output voltage for normal operation; the overall circuit structure is simple, with a hysteresis characteristic, and the temperature range configuration can be quickly completed by adjusting the resistance values of the third resistor and the fourth resistor, and the operation is simple. Description of the Drawings

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will further illustrate the present utility model in conjunction with the drawings and embodiments. The drawings in the following description are only partial embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts:

[0011] Figure 1 It is the circuit diagram of the operational amplifier and the voltage-dividing circuit of the over-temperature protection switch circuit of the preferred embodiment of the present utility model;

[0012] Figure 2 It is the circuit diagram of the voltage reference circuit of the over-temperature protection switch circuit of the preferred embodiment of the present utility model;

[0013] Figure 3 It is the MOS transistor circuit diagram of the over-temperature protection switch circuit of the preferred embodiment of the present utility model. Specific embodiments

[0014] In order to make the objectives, technical solutions and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be described clearly and completely below. Apparently, the described embodiments are some but not all of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present utility model.

[0015] The over-temperature protection switch circuit of the preferred embodiment of the present utility model, as Figure 1 shown, also refer to Figure 2 and Figure 3 , includes a voltage reference circuit 1, an operational amplifier U2, a voltage dividing circuit 3 and a MOS transistor Q1; the voltage reference circuit 1 is used to provide a reference voltage for the operational amplifier U2; the MOS transistor Q1 is used to control the output state of the power supply; the voltage dividing circuit 3 includes an NTC resistor R5, a first resistor R8 and a second resistor R12 connected in series in sequence; one end of the NTC resistor R5 far from the first resistor R8 is connected to the working power input terminal VIN, and one end of the second resistor R12 far from the first resistor R8 is grounded; one end of the first resistor R8 far from the NTC resistor R5 is connected to the negative input terminal of the operational amplifier U2; the positive input terminal of the operational amplifier U2 is connected with a third resistor R9 and a fourth resistor R6 in parallel, one end of the third resistor R9 far from the positive input terminal of the operational amplifier U2 is connected to the voltage reference circuit, and one end of the fourth resistor R6 far from the positive input terminal of the operational amplifier U2 is connected to the output terminal of the operational amplifier U2; the positive power input terminal of the operational amplifier U2 is connected to the working power input terminal, the negative power input terminal of the operational amplifier U2 is grounded, and the output terminal of the operational amplifier U2 is connected to the MOS transistor Q1;

[0016] During use, the inverting input terminal of operational amplifier U2 detects the voltage-dividing circuit composed of NTC resistor R5, first resistor R8, and second resistor R12. When the temperature rises, the voltage at the inverting input terminal of the operational amplifier gradually increases. When the temperature reaches the value set by third resistor R9 and fourth resistor R6, a low level is output, turning off MOS transistor Q1, thereby controlling the shutdown of the DCDC output voltage to protect the subsequent circuit. When the temperature drops, the voltage at the inverting input terminal of the operational amplifier gradually decreases. When the temperature reaches the value set by third resistor R9 and fourth resistor R6, a high level is output, turning on MOS transistor Q1, thereby controlling the opening of the DCDC output voltage to operate normally. The overall circuit structure is simple. While having a hysteresis characteristic, the temperature range configuration can be quickly completed by adjusting the resistance values of third resistor R9 and fourth resistor R6, and the operation is simple.

[0017] Among them, voltage reference circuit 1 includes voltage reference IC U1, fifth resistor R3 (current-limiting resistor), sixth resistor R7, seventh resistor R10, and capacitor (filter). The power supply pin of voltage reference IC U1 is electrically connected to fifth resistor R3, and the other end of fifth resistor R3 is connected to the working power supply input terminal. The ground pin of voltage reference IC U1 is grounded. The output pin of voltage reference IC U1 is connected to sixth resistor R7 and seventh resistor R10 in parallel. The other end of sixth resistor R7 is electrically connected to the power supply pin of voltage reference IC U1 and one end of the capacitor. The other end of seventh resistor R10 is electrically connected to the ground pin of voltage reference IC U1 and the other end of the capacitor. The other end of sixth resistor R7 is electrically connected to third resistor R9.

[0018] The voltage reference circuit of this solution uses a voltage reference IC. The reference voltage accuracy of the voltage reference IC is usually in the range of plus or minus 1%. Using the voltage reference IC can avoid the need to re-adjust the temperature range when the voltage at the working power supply input terminal VIN changes.

[0019] Preferably, the non-inverting input terminal of operational amplifier U2 is connected to eighth resistor R1 and ninth resistor R2 in parallel. The other end of eighth resistor R1 is connected to the working power supply input terminal, and the other end of ninth resistor R2 is grounded. The voltage is divided by eighth resistor R1 and ninth resistor R2 to provide power for operational amplifier U2.

[0020] Preferably, MOS transistor Q1 is an N-channel MOS transistor. The G pole of MOS transistor Q1 is connected to the output terminal of operational amplifier U2. The S pole of MOS transistor Q1 is connected to the DCDC power supply output terminal. The D pole of MOS transistor Q1 is connected to tenth resistor R4, and the other end of tenth resistor R4 is connected to the working power supply input terminal.

[0021] Among them, the value of R9 is usually within 1 kΩ. The value of R6 is adjusted according to R9. The sum of the values of R8 and R12 is usually not greater than twice the value of R5.

[0022] It should be understood that those of ordinary skill in the art can make improvements or modifications based on the above description, and all such improvements and modifications shall fall within the protection scope of the appended claims of this utility model.

Claims

1. An over-temperature protection switch circuit, characterized in that, It includes a voltage reference circuit, an operational amplifier, a voltage division circuit, and a MOS transistor; the voltage reference circuit is used to provide a reference voltage for the operational amplifier; the MOS transistor is used to control the output state of the power supply; the voltage division circuit includes an NTC resistor, a first resistor, and a second resistor connected in series in sequence; one end of the NTC resistor away from the first resistor is connected to the working power supply input terminal, and one end of the second resistor away from the first resistor is grounded; one end of the first resistor away from the NTC resistor is connected to the negative input terminal of the operational amplifier; the positive input terminal of the operational amplifier is connected with a third resistor and a fourth resistor in parallel, one end of the third resistor away from the positive input terminal of the operational amplifier is connected to the voltage reference circuit, and one end of the fourth resistor away from the positive input terminal of the operational amplifier is connected to the output terminal of the operational amplifier; the positive power supply input terminal of the operational amplifier is connected to the working power supply input terminal, the negative power supply input terminal of the operational amplifier is grounded, and the output terminal of the operational amplifier is connected to the MOS transistor.

2. The over-temperature protection switch circuit according to claim 1, characterized in that, The voltage reference circuit includes a voltage reference IC, a fifth resistor, a sixth resistor, a seventh resistor, and a capacitor; the power supply pin of the voltage reference IC is electrically connected to the fifth resistor, and the other end of the fifth resistor is connected to the working power supply input terminal; the ground pin of the voltage reference IC is grounded; the output pin of the voltage reference IC is connected with a sixth resistor and a seventh resistor in parallel, the other end of the sixth resistor is electrically connected to the power supply pin of the voltage reference IC and one end of the capacitor, and the other end of the seventh resistor is electrically connected to the ground pin of the voltage reference IC and the other end of the capacitor; the other end of the sixth resistor is electrically connected to the third resistor.

3. The over-temperature protection switch circuit according to claim 1 or 2, characterized in that, The positive input terminal of the operational amplifier is connected with an eighth resistor and a ninth resistor in parallel; the other end of the eighth resistor is connected to the working power supply input terminal, and the other end of the ninth resistor is grounded.

4. The over-temperature protection switch circuit according to claim 1, wherein The MOS transistor is an N-channel MOS transistor, the G pole of the MOS transistor is connected to the output terminal of the operational amplifier, the S pole of the MOS transistor is connected to the DCDC power supply output terminal, the D pole of the MOS transistor is connected to a tenth resistor, and the other end of the tenth resistor is connected to the working power supply input terminal.

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