Over-temperature protection circuit for high-voltage direct-current power supply

Abstract

The utility model discloses an over-temperature protection circuit for a high-voltage direct-current power supply, which is connected with a control circuit of the high-voltage direct-current power supply and comprises an input current sampling circuit and a power supply isolation conversion circuit which are connected with the control circuit, a temperature monitoring unit circuit connected with the input current sampling circuit, and a comparison circuit connected with the temperature monitoring unit circuit, and the protection trigger circuit is connected with the comparison circuit and the control circuit. According to the utility model, the input current sampling circuit is arranged to obtain current information when the high-voltage direct-current power supply works, a thermistor of the temperature monitoring unit circuit is utilized to detect the temperature of related current, and after a temperature signal is input to the comparison circuit, the comparison circuit generates a trigger signal to the protection trigger circuit, so that the high-voltage direct-current power supply is protected. The protection trigger circuit generates a protection signal to the control circuit to control the high-voltage direct-current power supply to trigger a protection mode in an over-temperature environment, so that the high-voltage direct-current power supply is prevented from having a fault due to high temperature, and the use stability of equipment is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of power supply circuits, and in particular relates to an over-temperature protection circuit for a high-voltage direct current power supply. Background Art

[0002] High-voltage DC power supply is a widely used electronic power supply. It converts AC mains or three-phase electricity into AC high voltage electricity through industrial frequency high-voltage transformer, and then rectifies and filters to obtain high-voltage DC power. High-voltage DC power supply is characterized by small size, light weight, high efficiency, high power, small ripple, low energy storage, high stability and high reliability. In order to meet the requirements of different uses, some DC high-voltage power supplies will be made into a form of voltage and current stabilization and automatic conversion.

[0003] Taking the high-voltage DC power supply used in oil logging instruments as an example, it is mentioned above that the high-voltage DC power supply is to step up the AC mains or three-phase electricity into AC high voltage electricity through the industrial frequency high-voltage transformer, and then rectify and filter to obtain high-voltage DC power. However, the problem caused by this solution is that the high-voltage DC power transformer is large in size, and the output filter capacitor capacity requirement is also relatively high. For the limited space inside the oil logging instrument, it is more troublesome to install. The high-voltage power supply using the high-frequency transformer switching power supply solution can be made small in size to meet the space requirements, but its high-temperature characteristics are difficult to meet the current environmental temperature requirements of up to 175°C in oil logging, which can easily lead to power failure and create safety hazards. Utility Model Content

[0004] The purpose of the utility model is to provide a high-voltage DC power supply over-temperature protection circuit, which mainly solves the problem that the existing high-voltage DC power supply is prone to failure due to excessive temperature in certain application scenarios and equipment (such as oil well logging instruments, aerospace high-speed aircraft, metallurgical electrical equipment, etc.).

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0006] A high-voltage DC power supply over-temperature protection circuit is connected to a control circuit of the high-voltage DC power supply, comprising an input current sampling circuit and a power isolation conversion circuit connected to the control circuit, a temperature monitoring unit circuit connected to the input current sampling circuit, a comparison circuit connected to the temperature monitoring unit circuit, and a protection trigger circuit connected to the comparison circuit and the control circuit;

[0007] The temperature monitoring unit circuit includes a thermistor RTC connected to the output pin of the input current sampling circuit, a resistor R1 connected to the other end of the thermistor RTC, and a capacitor C1 connected to the other end of the resistor R1 and grounded; wherein the other end of the resistor R1 is connected to the comparison circuit.

[0008] Furthermore, in the present invention, the input current sampling circuit includes a chip U1 of model INA282, a resistor R2 connected to the V-pin of the chip U1, resistors R3 and R4 connected to the other end of the resistor R2, an electrolytic capacitor C2 whose positive electrode is connected to the common end of the resistors R3 and R4 and whose negative electrode is grounded, an amplifier A1 whose in-phase input end is connected to the positive electrode of the electrolytic capacitor C2, a variable resistor R5 whose one fixed end is connected to the in-phase input end of the amplifier A1 and whose other fixed end is grounded, an amplifier A2 whose in-phase input end is connected to the free end of the variable resistor R5, and one end of the amplifier A1 is connected to the common end of the resistor R3 and R4. A resistor R6 is connected to the inverting input terminal and output terminal of the amplifier A1 and the other end is connected to the inverting input terminal of the amplifier A2, and a resistor R7 is connected to the inverting input terminal of the amplifier A2 at one end and the output terminal of the amplifier A2 at the other end; wherein, the V+ pin of the chip U1 is connected to the positive electrode of the 12V voltage source, the other end of the resistor R3 is connected to the negative electrode of the 12V voltage source, the other end of the resistor R4 is grounded, the positive and negative power supply terminals of the amplifier A2 are connected to the positive and negative electrodes of the 12V voltage source correspondingly, the output terminal of the amplifier A2 is connected to the thermistor RTC, and the -IN pin of the chip U1 is connected to the output terminal of the control circuit.

[0009] Furthermore, in the utility model, the power isolation conversion circuit includes a transformer U2 whose VS pin is connected to the control circuit, a capacitor C5 whose one end is connected to the VC pin of the transformer U4 and the other end is grounded, a diode D1 whose positive electrode is connected to the VP pin of the transformer U2, and a capacitor C6 whose one end is connected to the cathode of the diode D1 and the other end is grounded; wherein the cathode of the diode D1 is also connected to the comparison circuit and the protection trigger circuit.

[0010] Further, in the present invention, the comparison circuit includes a resistor R8 connected to the other end of the resistor R1, a resistor R7 connected to the other end of the resistor R8 and grounded, an operational amplifier A3 whose inverting input end is connected to the common end of the resistors R7 and R8, a resistor R9 connected to the inverting input end of the operational amplifier A3, a capacitor C4 whose one end is connected to the other end of the resistor R9 and grounded, a resistor R11 connected between the inverting input end and the output end of the operational amplifier A3, a switch S1 connected to the inverting input end of the operational amplifier A3, a capacitor C3 whose one end is connected to the other end of the switch S1 and grounded, and a resistor R10 whose one end is connected to the common end of the switch S1 and the capacitor C3 and whose other end is connected to the output end of the operational amplifier A3; wherein the other end of the resistor R8 is connected to the negative electrode of the 12V voltage source, and the output end of the operational amplifier A3 is also connected to the negative electrode of the protection trigger circuit and the diode D1 through the resistor R12 as the output end of the comparison circuit.

[0011] Furthermore, in the utility model, the protection trigger circuit includes an operational amplifier A4 whose inverting input terminal is connected to the other end of the resistor R12 and whose non-inverting input terminal is connected to the reference voltage VREF via the resistor R13, a resistor R15 connected between the output terminal and the inverting input terminal of the operational amplifier A4, a resistor R14 having one end connected to the reverse input terminal of the operational amplifier A4 and the other end grounded, and a resistor R16 having one end connected to the output terminal of the operational amplifier A4 and the other end grounded; wherein the output terminal of the operational amplifier A4 is connected to the control circuit.

[0012] Compared with the prior art, the utility model has the following beneficial effects:

[0013] (1) The utility model obtains the current information of the high-voltage DC power supply when it is working by setting an input current sampling circuit, and uses the thermistor of the temperature monitoring unit circuit to detect the temperature of the relevant current. After the temperature signal is input to the comparison circuit, the comparison circuit generates a trigger signal to the protection trigger circuit, and the protection trigger circuit generates a protection signal to the control circuit, which controls the high-voltage DC power supply to trigger the protection mode in an over-temperature environment, thereby avoiding the high-voltage DC power supply from malfunctioning due to high temperature and improving the stability of the equipment.

[0014] (2) The temperature monitoring unit circuit of the utility model adopts a temperature-sensitive thermistor RTC to detect the operating temperature of the high-voltage DC power supply. When the thermistor RTC detects that the operating current or the ambient temperature gradually increases to a preset temperature value, the resistance of the negative temperature coefficient thermistor RTC also drops to a certain value, and the temperature detection circuit outputs a signal to the comparison circuit. At the same time, in this circuit, the output signal of the temperature monitoring unit circuit is filtered by the resistor R1 and the capacitor C1 and then input into the comparison circuit, thereby making the output signal more accurate and reliable.

[0015] (3) The utility model sets an input current sampling circuit and uses the current sampling chip INA282 to sample the current signal from the control circuit of the high-voltage DC power supply. The sampled current signal is filtered by the resistor R4 and the capacitor C2, and then the amplifiers A1 and A2 perform two-stage amplification of the sampling signal, thereby making the sensitivity of the entire sampling circuit higher and improving the current sampling accuracy of the high-voltage DC power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the circuit structure of the utility model. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The present invention includes but is not limited to the following embodiments.

[0018] Example

[0019] like Figure 1 As shown, a high-voltage DC power supply over-temperature protection circuit disclosed in the utility model is connected to the control circuit of the high-voltage DC power supply, including an input current sampling circuit and a power isolation conversion circuit connected to the control circuit, a temperature monitoring unit circuit connected to the input current sampling circuit, a comparison circuit connected to the temperature monitoring unit circuit, and a protection trigger circuit connected to the comparison circuit and the control circuit.

[0020] The input current sampling circuit is mainly used to obtain the working current information of the high-voltage DC power supply when it is working. The temperature monitoring unit circuit monitors the temperature information from the working current information and sends the temperature signal to the comparison circuit. After comparing the comparison circuit with the threshold temperature, the trigger signal is output to the protection trigger circuit. The protection trigger circuit generates a protection signal to the control circuit to control the high-voltage DC power supply to trigger the protection mode in an over-temperature environment, thereby avoiding failure of the high-voltage DC power supply due to high temperature and improving the stability of the use of oil logging instruments.

[0021] In this embodiment, the temperature monitoring unit circuit includes a thermistor RTC connected to the output pin of the input current sampling circuit, a resistor R1 connected to the other end of the thermistor RTC, and a capacitor C1 connected to the other end of the resistor R1 and grounded; wherein the other end of the resistor R1 is connected to the comparison circuit. When the thermistor RTC detects that the working current or the ambient temperature gradually increases to a preset temperature value, the resistance value of the negative temperature coefficient thermistor RTC also decreases to a certain value. At the same time, in this circuit, the output signal of the temperature monitoring unit circuit is filtered by the resistor R1 and the capacitor C1 and then input into the comparison circuit, so that the output signal is more accurate and reliable.

[0022] In this embodiment, the input current sampling circuit includes a chip U1 of model INA282, a resistor R2 connected to the V-pin of the chip U1, resistors R3 and R4 connected to the other end of the resistor R2, an electrolytic capacitor C2 whose positive electrode is connected to the common end of the resistors R3 and R4 and whose negative electrode is grounded, an amplifier A1 whose in-phase input end is connected to the positive electrode of the electrolytic capacitor C2, a variable resistor R5 whose one fixed end is connected to the in-phase input end of the amplifier A1 and whose other fixed end is grounded, an amplifier A2 whose in-phase input end is connected to the free end of the variable resistor R5, and one end of the amplifier A1 connected to the inverting input end of the amplifier A1. The input and output ends of the chip U1 are connected and the other end is connected to the inverting input end of the amplifier A2. The resistor R6, one end of which is connected to the inverting input end of the amplifier A2 and the other end is connected to the output end of the amplifier A2; wherein the V+ pin of the chip U1 is connected to the positive pole of the 12V voltage source, the other end of the resistor R3 is connected to the negative pole of the 12V voltage source, the other end of the resistor R4 is grounded, the positive and negative power supply ends of the amplifier A2 are connected to the positive and negative poles of the 12V voltage source respectively, the output end of the amplifier A2 is connected to the thermistor RTC, and the -IN pin of the chip U1 is connected to the output end of the control circuit. The circuit uses the current sampling chip INA282 to sample the current signal from the control circuit of the high-voltage DC power supply. The sampled current signal is filtered by the resistor R4 and the capacitor C2, and then the sampling signal is amplified in two stages by the amplifiers A1 and A2, so that the sensitivity of the entire sampling circuit is higher, and the current sampling accuracy of the high-voltage DC power supply is improved.

[0023] In this embodiment, the power isolation conversion circuit includes a transformer U2 whose VS pin is connected to the control circuit, a capacitor C5 whose one end is connected to the VC pin of the transformer U4 and the other end is grounded, a diode D1 whose positive electrode is connected to the VP pin of the transformer U2, and a capacitor C6 whose one end is connected to the negative electrode of the diode D1 and the other end is grounded; wherein the negative electrode of the diode D1 is also connected to the comparison circuit and the protection trigger circuit. The power isolation conversion circuit is used to transform the isolation voltage of the power input, and the transformer is selected to be a transformer that is resistant to high temperature and suitable for high voltage power supply. The transformer of the high temperature resistant high voltage power supply meets the special high temperature environment in which it is used, and minimizes the loss of output power.

[0024] In this embodiment, the comparison circuit includes a resistor R8 connected to the other end of the resistor R1, a resistor R7 connected to the other end of the resistor R8 and grounded, an operational amplifier A3 whose inverting input terminal is connected to the common end of the resistors R7 and R8, a resistor R9 connected to the inverting input terminal of the operational amplifier A3, a capacitor C4 whose one end is connected to the other end of the resistor R9 and grounded, a resistor R11 connected between the inverting input terminal and the output terminal of the operational amplifier A3, a switch S1 connected to the inverting input terminal of the operational amplifier A3, a capacitor C3 whose one end is connected to the other end of the switch S1 and grounded, and a resistor R10 whose one end is connected to the common end of the switch S1 and the capacitor C3 and whose other end is connected to the output terminal of the operational amplifier A3; wherein the other end of the resistor R8 is connected to the negative electrode of the 12V voltage source, and the output terminal of the operational amplifier A3 is also connected to the protection trigger circuit and the negative electrode of the diode D1 through the resistor R12 as the output terminal of the comparison circuit. The comparison circuit generates a trigger signal to the protection trigger circuit according to the preset temperature threshold information by comparing the current signal from the temperature monitoring unit circuit with the input reference signal.

[0025] In this embodiment, the protection trigger circuit includes an operational amplifier A4 whose inverting input terminal is connected to the other end of the resistor R12 and whose non-inverting input terminal is connected to the reference voltage VREF via the resistor R13, a resistor R15 connected between the output terminal and the inverting input terminal of the operational amplifier A4, a resistor R14 whose one end is connected to the reverse input terminal of the operational amplifier A4 and whose other end is grounded, and a resistor R16 whose one end is connected to the output terminal of the operational amplifier A4 and whose other end is grounded; wherein the output terminal of the operational amplifier A4 is connected to the control circuit. The protection trigger circuit receives a trigger signal from the comparison circuit and generates a control signal to the control circuit to realize over-temperature protection control of the high-voltage DC power supply.

[0026] Through the above design, the utility model obtains the current information of the high-voltage DC power supply when it is working by setting an input current sampling circuit, and uses the thermistor of the temperature monitoring unit circuit to detect the temperature of the relevant current, and after the temperature signal is input to the comparison circuit, the comparison circuit generates a trigger signal to the protection trigger circuit, and the protection trigger circuit generates a protection signal to the control circuit, which controls the high-voltage DC power supply to trigger the protection mode in an over-temperature environment to avoid the high-voltage DC power supply from malfunctioning due to high temperature. The over-temperature protection circuit is suitable for oil well logging instruments in oil production, high-speed aircraft in the aerospace field, and high-temperature DC power supplies for electrical equipment in the metallurgical field.

[0027] The above embodiment is only one of the preferred implementation modes of the present utility model and should not be used to limit the protection scope of the present utility model. Any changes or modifications that are made to the main design concept and spirit of the present utility model without any substantive significance, as long as the technical problems solved are still consistent with the present utility model, should be included in the protection scope of the present utility model.

Claims

1. A high-voltage direct current power supply over-temperature protection circuit, connected to a control circuit of the high-voltage direct current power supply, characterized in that: It includes an input current sampling circuit and a power supply isolation conversion circuit connected to the control circuit, a temperature monitoring unit circuit connected to the input current sampling circuit, a comparison circuit connected to the temperature monitoring unit circuit, and a protection trigger circuit connected to the comparison circuit and the control circuit; The temperature monitoring unit circuit includes a thermistor RTC connected to the output pin of the input current sampling circuit, a resistor R1 connected to the other end of the thermistor RTC, and a capacitor C1 connected to the other end of the resistor R1 and grounded; wherein the other end of the resistor R1 is connected to the comparison circuit.

2. A high voltage DC power supply over-temperature protection circuit according to claim 1, characterized in that: The input current sampling circuit includes a chip U1 of model INA282, a resistor R2 connected to the V-pin of the chip U1, resistors R3 and R4 connected to the other end of the resistor R2, an electrolytic capacitor C2 whose positive electrode is connected to the common end of the resistors R3 and R4 and whose negative electrode is grounded, an amplifier A1 whose in-phase input end is connected to the positive electrode of the electrolytic capacitor C2, a variable resistor R5 whose one fixed end is connected to the in-phase input end of the amplifier A1 and whose other fixed end is grounded, an amplifier A2 whose in-phase input end is connected to the free end of the variable resistor R5, and one end of the in-phase input end of the amplifier A1 is connected to the inverting input end of the amplifier A1. A resistor R6 is connected to both the positive and negative power supply terminals of the amplifier A2 and the other end is connected to the inverting input terminal of the amplifier A2, and a resistor R7 is connected to the inverting input terminal of the amplifier A2 at one end and the output terminal of the amplifier A2 at the other end; wherein, the V+ pin of the chip U1 is connected to the positive electrode of the 12V voltage source, the other end of the resistor R3 is connected to the negative electrode of the 12V voltage source, the other end of the resistor R4 is grounded, the positive and negative power supply terminals of the amplifier A2 are correspondingly connected to the positive and negative electrodes of the 12V voltage source, the output terminal of the amplifier A2 is connected to the thermistor RTC, and the -IN pin of the chip U1 is connected to the output terminal of the control circuit.

3. A high voltage DC power supply over-temperature protection circuit according to claim 2, characterized in that: The power isolation conversion circuit includes a transformer U2 whose VS pin is connected to the control circuit, a capacitor C5 whose one end is connected to the VC pin of the transformer U4 and the other end is grounded, a diode D1 whose positive electrode is connected to the VP pin of the transformer U2, and a capacitor C6 whose one end is connected to the cathode of the diode D1 and the other end is grounded; wherein the cathode of the diode D1 is also connected to the comparison circuit and the protection trigger circuit.

4. The high voltage DC power supply over-temperature protection circuit according to claim 3, characterized in that: The comparison circuit includes a resistor R8 connected to the other end of the resistor R1, a resistor R7 connected to the other end of the resistor R8 and grounded, an operational amplifier A3 whose inverting input end is connected to the common end of the resistors R7 and R8, a resistor R9 connected to the inverting input end of the operational amplifier A3, a capacitor C4 whose one end is connected to the other end of the resistor R9 and grounded, a resistor R11 connected between the inverting input end and the output end of the operational amplifier A3, a switch S1 connected to the inverting input end of the operational amplifier A3, a capacitor C3 whose one end is connected to the other end of the switch S1 and grounded, and a resistor R10 whose one end is connected to the common end of the switch S1 and the capacitor C3 and whose other end is connected to the output end of the operational amplifier A3; wherein the other end of the resistor R8 is connected to the negative electrode of the 12V voltage source, and the output end of the operational amplifier A3 is also connected to the protection trigger circuit and the negative electrode of the diode D1 through the resistor R12 as the output end of the comparison circuit.

5. The high voltage DC power supply over-temperature protection circuit according to claim 4, characterized in that: The protection trigger circuit includes an operational amplifier A4 whose inverting input terminal is connected to the other end of the resistor R12 and whose non-inverting input terminal is connected to the reference voltage VREF via the resistor R13, a resistor R15 connected between the output terminal and the inverting input terminal of the operational amplifier A4, a resistor R14 having one end connected to the reverse input terminal of the operational amplifier A4 and the other end grounded, and a resistor R16 having one end connected to the output terminal of the operational amplifier A4 and the other end grounded; wherein the output terminal of the operational amplifier A4 is connected to the control circuit.

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