Multi-path over-temperature detection circuit based on ideal diode circuit

Abstract

The utility model relates to the technical field of over-temperature detection circuits, in particular to a multipath over-temperature detection circuit based on an ideal diode circuit, which comprises a temperature sampling and ideal diode circuit, a voltage following circuit, a second operational amplifier and an MCU (Microprogrammed Control Unit) which are connected with one another, the inverting input end of the second operational amplifier is connected with a preset reference voltage circuit, and the output end of the second operational amplifier is connected with the MCU. The circuit is simple in structure and low in cost; and the temperature can be accurately monitored, so that accurate control can be conveniently realized, and the purpose of protecting the circuit is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of overtemperature detection circuits, and particularly relates to a multi-channel overtemperature detection circuit based on an ideal diode circuit. Background Art

[0002] A large number of power devices are applied in industrial automation systems. With the increasing integration and power consumption of power devices, if they are used for a long time or in the case of short circuit and excessive current, the device temperature will rise rapidly. A relatively high temperature will cause the power device to fail to work properly or even damage the circuit. Therefore, it is necessary to detect in real time and accurately whether the temperature will exceed the normal operating temperature of the device, and send information to the control end when overtemperature occurs, so as to protect the circuit in time.

[0003] In power devices such as IGBT modules, due to the complex on-site application conditions, if a load short circuit occurs, the instantaneous large current will cause the internal temperature of the device to rise rapidly. The existing multi-channel temperature detection circuit uses three thermistors to detect the temperature of the power device beside the device to be measured, and the voltage of the thermistor will change proportionally with the temperature. When the device temperature exceeds the preset temperature (that is, when the resistance voltage division value exceeds the preset voltage value), the circuit will send a level signal to the control end, and the control end will judge whether to perform overtemperature protection.

[0004] The existing scheme has a complex circuit structure, and a prefabricated circuit needs to be set up at the control end to compare the actual sampled voltage, which is difficult to calculate and has a high cost. And it only directly outputs the voltage through the form of resistance sampling without signal processing, so the sampling accuracy is low and it is easy to be mis-triggered. This will lead to misjudgment at the control end and miss the best time to trigger overtemperature protection.

[0005] Therefore, there is an urgent need for a new technical solution to solve the above technical problems. Summary of the Utility Model

[0006] The purpose of the utility model is to overcome the problems of the above existing technology, and provides a multi-channel overtemperature detection circuit based on an ideal diode circuit, which is used to solve the technical problems that the existing scheme has a complex circuit structure, a prefabricated circuit needs to be set up at the control end to compare the actual sampled voltage, resulting in great calculation difficulty; and it directly outputs the voltage through the form of resistance sampling without signal processing, so the sampling accuracy is low and it is easy to be mis-triggered, resulting in misjudgment at the control end and missing the best time to trigger overtemperature protection.

[0007] The above purpose is achieved by the following technical solutions:

[0008] A multi-channel over-temperature detection circuit based on an ideal diode circuit, comprising a temperature sampling and ideal diode circuit, a voltage follower circuit, a second operational amplifier and an MCU connected to each other. The non-inverting input terminal of the second operational amplifier is connected to the voltage follower circuit, the inverting input terminal of the second operational amplifier is connected to a preset reference voltage circuit, and the output terminal of the second operational amplifier is connected to the MCU.

[0009] Further, the temperature sampling and ideal diode circuit includes a first temperature sampling and ideal diode circuit, a second temperature sampling and ideal diode circuit, and a third temperature sampling and ideal diode circuit connected in parallel with each other.

[0010] Further, the first temperature sampling and ideal diode circuit includes a forty-eighth resistor, a forty-ninth resistor and a fiftieth resistor connected in series with each other, and is connected to the non-inverting input terminal of an eighth operational amplifier. The output terminal of the eighth operational amplifier is connected to the anode of an eighth diode, and the cathode of the eighth diode is connected to the voltage follower circuit. The second temperature sampling and ideal diode circuit includes a thirty-eighth resistor, a thirty-ninth resistor and a fortieth resistor connected in series with each other, and is connected to the non-inverting input terminal of a fifth operational amplifier. The output terminal of the fifth operational amplifier is connected to the anode of a fifth diode, and the cathode of the fifth diode is connected to the voltage follower circuit. The third temperature sampling and ideal diode circuit includes a forty-third resistor, a forty-fourth resistor and a forty-fifth resistor connected in series with each other, and is connected to the non-inverting input terminal of a seventh operational amplifier. The output terminal of the seventh operational amplifier is connected to the anode of a seventh diode, and the cathode of the seventh diode is connected to the voltage follower circuit.

[0011] Further, the cathode of the eighth diode is connected to the inverting input terminal of the eighth operational amplifier, the cathode of the fifth diode is connected to the inverting input terminal of the fifth operational amplifier, and the cathode of the seventh diode is connected to the inverting input terminal of the seventh operational amplifier.

[0012] Further, the voltage follower circuit includes a first operational amplifier. A second resistor is connected to the non-inverting input terminal of the first operational amplifier, and the other end of the second resistor is connected to the cathodes of the eighth diode, the fifth diode and the seventh diode. The output terminal of the first operational amplifier is connected to the inverting input terminal of the first operational amplifier. The output terminal of the first operational amplifier is also connected to one end of a third resistor, and the other end of the third resistor is connected to the non-inverting input terminal of the second operational amplifier.

[0013] Further, a first capacitor is provided between the second resistor and the non-inverting input terminal of the first operational amplifier, and the other end of the first capacitor is grounded; a second capacitor is provided between the third resistor and the non-inverting input terminal of the second operational amplifier, and the other end of the second capacitor is grounded.

[0014] Further, the preset reference voltage circuit includes a sixth operational amplifier. The non-inverting input terminal of the sixth operational amplifier is connected to a series voltage dividing circuit. The output terminal of the sixth operational amplifier is connected to the anode of a sixth diode, and the cathode of the sixth diode is connected to the inverting input terminal of the second operational amplifier.

[0015] Further, a forty-sixth resistor and a fourth capacitor are connected in parallel between the cathode of the sixth diode and the inverting input terminal of the second operational amplifier.

[0016] Further, the series voltage dividing circuit includes a fifth resistor and a fifty-third resistor connected in parallel and connected to a power supply, and a ninth resistor and a forty-first resistor connected in parallel.

[0017] A multi-path over-temperature detection circuit based on an ideal diode circuit provided by the present invention not only has a simple structure and low cost, but also can accurately monitor the temperature, thereby facilitating accurate control and achieving the purpose of protecting the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A circuit diagram of a multi-path over-temperature detection circuit based on an ideal diode circuit according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The present invention will be further described in detail below with reference to the drawings and embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. 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 invention.

[0020] As Figure 1 shown, a multi-path over-temperature detection circuit based on an ideal diode circuit includes a temperature sampling and ideal diode circuit, a voltage follower circuit, a second operational amplifier U2 and an MCU connected to each other. The non-inverting input terminal of the second operational amplifier U2 is connected to the voltage follower circuit. The inverting input terminal of the second operational amplifier U2 is connected to a preset reference voltage circuit. The output terminal of the second operational amplifier U2 is connected to the MCU.

[0021] Working principle:

[0022] The temperature sampling and ideal diode circuit receive the temperature change emitted by the heat source at the corresponding sampling point. The temperature change is converted into voltage data through the voltage division of the thermistor. Among them, the diode in the path with the highest sampling point voltage conducts, and the voltage is input to the second operational amplifier U2 after stabilizing the voltage through the voltage follower circuit. The 5V power supply voltage is series-divided by two groups of parallel resistors to obtain a preset reference voltage, which is input to the inverting input terminal of the second operational amplifier U2, and high and low levels are output. After passing through the level conversion circuit, it is input to the MCU.

[0023] It should be noted that the operational amplifiers used in each circuit in this embodiment are all OPA2343.

[0024] In this embodiment, the temperature sampling and ideal diode circuit includes a first temperature sampling and ideal diode circuit, a second temperature sampling and ideal diode circuit, and a third temperature sampling and ideal diode circuit that are connected in parallel with each other.

[0025] Specifically, the first temperature sampling and ideal diode circuit includes a forty-eighth resistor R48, a forty-ninth resistor R49, and a fiftieth resistor R50 that are connected in series with each other, and is connected to the non-inverting input terminal of the eighth operational amplifier U8. The output terminal of the eighth operational amplifier U8 is connected to the anode of the eighth diode D8. The cathode of the eighth diode D8 is connected to the voltage follower circuit;

[0026] The second temperature sampling and ideal diode circuit includes a thirty-eighth resistor R38, a thirty-ninth resistor R39, and a fortieth resistor R40 that are connected in series with each other, and is connected to the non-inverting input terminal of the fifth operational amplifier U5. The output terminal of the fifth operational amplifier U5 is connected to the anode of the fifth diode D5. The cathode of the fifth diode D5 is connected to the voltage follower circuit;

[0027] The third temperature sampling and ideal diode circuit includes a forty-third resistor R43, a forty-fourth resistor R44, and a forty-fifth resistor R45 that are connected in series with each other, and is connected to the non-inverting input terminal of the seventh operational amplifier U7. The output terminal of the seventh operational amplifier U7 is connected to the anode of the seventh diode D7. The cathode of the seventh diode D7 is connected to the voltage follower circuit.

[0028] In addition, the cathode of the eighth diode D8 is connected to the inverting input terminal of the eighth operational amplifier U8, the cathode of the fifth diode D5 is connected to the inverting input terminal of the fifth operational amplifier U5, and the cathode of the seventh diode D7 is connected to the inverting input terminal of the seventh operational amplifier U7.

[0029] In this embodiment, when the inverting input terminal of the operational amplifier is connected to the output terminal, an inverting amplifier is formed. This amplifier stabilizes the output signal through a negative feedback mechanism to ensure that the output is opposite in phase to the input signal.

[0030] In this embodiment, the temperature sampling and ideal diode circuit can use common NTC, PTC thermistors, etc. on the market.

[0031] The positive pole of the diode in this circuit is connected to the output terminal of the operational amplifier, and the negative pole is connected to the inverting terminal of the operational amplifier. According to the virtual short and virtual open properties of the operational amplifier, the voltage V at the negative pole of the diode d1- is equal to the voltage V at the non-inverting terminal 1+ . Since the thermistor changes non-linearly with temperature, the temperature value can be converted into voltage. Assuming that the voltage V of the first path 1+ is relatively high, then V 1+ >V 2+ , V 1+ >V 3+ . The operational amplifier forms feedback, showing virtual short, V d1 - = V 1+ . The negative poles of the diodes are together with V d1 - = V d2 - = V d3- , that is, V d2- >V 2+ , V d3- >V 3+ . Then the first path diode conducts, and the positive poles of the second and third path diodes are at a low voltage close to zero, and the negative poles of the diodes are V d2- , V d3- . The diodes are cut off.

[0032] When V 2+ rises above V 1+ , because at this time V d1 - = V d2 - = V d3- , then V 2+ >V d2- . The second path diode conducts to form feedback, V d2 - = V 2+ , V 2+ = V d2 - = V d3- . Similarly, the outputs of the first and third path operational amplifiers are at low voltages, and the diodes are cut off.

[0033] This enables only the path with a significant temperature change among multiple paths of temperature detection to be input into the comparison circuit.

[0034] In this embodiment, the voltage follower circuit includes a first operational amplifier U1. The non-inverting input terminal of the first operational amplifier U1 is connected to a second resistor R2. The other end of the second resistor R2 is connected to the cathode of the eighth diode D8, the cathode of the fifth diode D5, and the cathode of the seventh diode D7.

[0035] The output terminal of the first operational amplifier U1 is connected to the inverting input terminal of the first operational amplifier U1.

[0036] The output terminal of the first operational amplifier U1 is also connected to one end of a third resistor R3. The other end of the third resistor R3 is connected to the non-inverting input terminal of the second operational amplifier U2.

[0037] A first capacitor C1 is provided between the second resistor R2 and the non-inverting input terminal of the first operational amplifier U1. The other end of the first capacitor C1 is grounded.

[0038] A second capacitor C2 is provided between the third resistor R3 and the non-inverting input terminal of the second operational amplifier U2. The other end of the second capacitor C2 is grounded.

[0039] Specifically, through this voltage follower circuit, according to the virtual short property of the operational amplifier, the voltage at the non-inverting input terminal is made equal to the voltage at the output terminal, thus forming a voltage stabilization circuit.

[0040] In this embodiment, the preset reference voltage circuit includes a sixth operational amplifier U6. The non-inverting input terminal of the sixth operational amplifier U6 is connected to a series voltage dividing circuit. The output terminal of the sixth operational amplifier U6 is connected to the anode of the sixth diode D6. The cathode of the sixth diode D6 is connected to the inverting input terminal of the second operational amplifier U2, and the cathode of the sixth diode D6 is also connected to the inverting input terminal of the sixth operational amplifier U6.

[0041] Specifically, it is mainly composed of the series voltage division of two pairs of parallel resistors and an ideal diode circuit. The resistance values of each resistor are calculated from the ratio of the resistance value of the thermistor at a preset temperature to the pull-down resistor.

[0042] The preset voltage and the sampled voltage are input to the operational amplifier for comparison, and then high and low levels are output.

[0043] Among them, the series voltage dividing circuit includes a fifth resistor R5 and a fifty-third resistor R53 connected in parallel with each other and connected to the power supply VCC, and a ninth resistor R9 and a forty-first resistor R41 connected in parallel with each other.

[0044] In addition, a forty-sixth resistor R46 and a fourth capacitor C4 are connected in parallel between the cathode of the sixth diode D6 and the inverting input terminal of the second operational amplifier U2.

[0045] The above is only to illustrate the implementation manners of the present utility model and is not intended to limit the present utility model. For those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A multi-path over-temperature detection circuit based on an ideal diode circuit, characterized in that: The invention comprises a temperature sampling and ideal diode circuit, a voltage follower circuit, a second operational amplifier (U2) and an MCU which are connected to each other, wherein the in-phase input terminal of the second operational amplifier (U2) is connected to the voltage follower circuit, the inverting input terminal of the second operational amplifier (U2) is connected to a preset reference voltage circuit, and the output terminal of the second operational amplifier (U2) is connected to the MCU.

2. The multi-path over-temperature detection circuit based on an ideal diode circuit according to claim 1, characterized in that: The temperature sampling and ideal diode circuit comprises a first temperature sampling and ideal diode circuit, a second temperature sampling and ideal diode circuit and a third temperature sampling and ideal diode circuit which are connected in parallel with each other.

3. The multi-path over-temperature detection circuit based on an ideal diode circuit according to claim 2, characterized in that: The first temperature sampling and ideal diode circuit comprises a forty-eighth resistor (R48), a forty-ninth resistor (R49) and a fiftieth resistor (R50) connected in series with each other, and connected to the non-inverting input terminal of the eighth operational amplifier (U8), the output terminal of the eighth operational amplifier (U8) is connected to the anode of the eighth diode (D8), and the cathode of the eighth diode (D8) is connected to the voltage follower circuit; The second temperature sampling and ideal diode circuit comprises a thirty-eighth resistor (R38), a thirty-ninth resistor (R39) and a fortieth resistor (R40) connected in series with each other, and connected to the non-inverting input terminal of the fifth operational amplifier (U5), the output terminal of the fifth operational amplifier (U5) is connected to the anode of the fifth diode (D5), and the cathode of the fifth diode (D5) is connected to the voltage follower circuit; The third temperature sampling and ideal diode circuit comprises a forty-third resistor (R43), a forty-fourth resistor (R44) and a forty-fifth resistor (R45) connected in series with each other, and is connected to the non-inverting input terminal of the seventh operational amplifier (U7), the output terminal of the seventh operational amplifier (U7) is connected to the anode of the seventh diode (D7), and the cathode of the seventh diode (D7) is connected to the voltage follower circuit.

4. The multi-path over-temperature detection circuit based on an ideal diode circuit according to claim 3, characterized in that: The cathode of the eighth diode (D8) is connected to the reverse input terminal of the eighth operational amplifier (U8), the cathode of the fifth diode (D5) is connected to the reverse input terminal of the fifth operational amplifier (U5), and the cathode of the seventh diode (D7) is connected to the reverse input terminal of the seventh operational amplifier (U7).

5. The multi-path over-temperature detection circuit based on an ideal diode circuit according to claim 3, characterized in that: The voltage follower circuit comprises a first operational amplifier (U1), a non-inverting input terminal of the first operational amplifier (U1) is connected to a second resistor (R2), and the other end of the second resistor (R2) is connected to the cathode of the eighth diode (D8), the cathode of the fifth diode (D5), and the cathode of the seventh diode (D7); The output terminal of the first operational amplifier (U1) is connected to the inverting input terminal of the first operational amplifier (U1); The output end of the first operational amplifier (U1) is also connected to one end of a third resistor (R3), and the other end of the third resistor (R3) is connected to the in-phase input end of the second operational amplifier (U2).

6. The multi-path over-temperature detection circuit based on an ideal diode circuit according to claim 5, characterized in that: A first capacitor (C1) is provided between the second resistor (R2) and the common-phase input terminal of the first operational amplifier (U1), and the other end of the first capacitor (C1) is grounded; A second capacitor (C2) is provided between the third resistor (R3) and the non-inverting input terminal of the second operational amplifier (U2), and the other end of the second capacitor (C2) is grounded.

7. The multi-path over-temperature detection circuit based on an ideal diode circuit according to claim 1, characterized in that: The preset reference voltage circuit comprises a sixth operational amplifier (U6), a non-inverting input terminal of the sixth operational amplifier (U6) is connected to a series voltage divider circuit, an output terminal of the sixth operational amplifier (U6) is connected to an anode of a sixth diode (D6), and a cathode of the sixth diode (D6) is connected to an inverting input terminal of the second operational amplifier (U2).

8. The multi-path over-temperature detection circuit based on an ideal diode circuit according to claim 7, characterized in that: A forty-sixth resistor (R46) and a fourth capacitor (C4) are also connected in parallel between the cathode of the sixth diode (D6) and the inverting input terminal of the second operational amplifier (U2).

9. A multi-path over-temperature detection circuit based on an ideal diode circuit according to claim 7 or 8, characterized in that: The series voltage divider circuit includes a fifth resistor (R5) and a fifty-third resistor (R53) connected in parallel to each other and connected to a power source (VCC), and a ninth resistor (R9) and a forty-first resistor (R41) connected in parallel to each other.

Images