Temperature sampling protection circuit with hysteresis of isolated power supply

Abstract

The utility model relates to the technical field of isolated power supplies, and discloses a temperature sampling protection circuit with hysteresis of an isolated power supply, the temperature sampling protection circuit with hysteresis comprises a temperature sampling circuit, a voltage reference circuit, a voltage comparison circuit, a hysteresis circuit and an optical coupler isolation circuit, the voltage comparison circuit comprises a voltage comparison chip U2A, and the hysteresis circuit comprises an optical coupler isolation circuit. The model number of the voltage comparison chip U2A is LM393DR2G; according to the temperature sampling protection circuit with hysteresis of the isolated power supply, through the arrangement of the hysteresis circuit and the optical coupler isolation circuit, when an input signal reaches a set threshold value, an output signal is overturned, and after the input signal leaves the set threshold value, the output signal is kept in a state after overturning until the input signal reaches another threshold value, and the output is overturned again, so that the output signal is kept in a state after overturning. The high-low level output by the voltage comparison circuit is subjected to optocoupler isolation, a high or low level is output and input to the single-chip microcomputer, and whether over-temperature protection exists or not is judged, and whether over-temperature protection is removed or not is judged.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of isolated power supply, concretely to a temperature sampling protection circuit with hysteresis of isolated power supply. BACKGROUND

[0002] In industrial control equipment, sometimes the power ground between two systems is required to be isolated, such as isolating ground noise, isolating high common mode voltage, etc. A DC converter with a transformer is used to separate the two power supplies, making them independent of each other.

[0003] In some existing isolated power supplies, there is usually only a single-chip microcomputer on one side, which can only sample temperature data on the same side, while the other side may overheat and cannot be protected, leading to device failure and even fire. Alternatively, it only determines the over-temperature value through simple high and low level judgment, but cannot determine the temperature drop and remove the over-temperature protection. In view of this, the utility model provides a temperature sampling protection circuit with hysteresis of isolated power supply. UTILITY MODEL CONTENTS

[0004] The utility model aims at providing a temperature sampling protection circuit with hysteresis of isolated power supply to solve the problems in the background art.

[0005] To achieve the above-mentioned purpose, the utility model provides the following technical scheme: a temperature sampling protection circuit with hysteresis of isolated power supply, which comprises a temperature sampling circuit, a voltage reference circuit, a voltage comparison circuit, a hysteresis circuit and an optocoupler isolation circuit.

[0006] Optionally, the voltage comparison circuit comprises a voltage comparison chip U2A, and the model of the voltage comparison chip U2A is LM393DR2G.

[0007] Optionally, the temperature sampling circuit comprises a resistor R6 and a resistor R8, one end of the resistor R6 is electrically connected with the end 2 of the voltage comparison chip U2A, the other end of the resistor R6 is grounded, one end of the resistor R8 is electrically connected with the end 2 of the voltage comparison chip U2A, the other end of the resistor R8 is electrically connected with the end 12V, the end 1 of the voltage comparison chip U2A is electrically connected with one end of a resistor R5, the other end of the resistor R5 is electrically connected with an OTP end, the resistor R5 is electrically connected with one end of a capacitor C4, and the other end of the capacitor C4 is grounded.

[0008] Optionally, the voltage reference circuit comprises a resistor R1 and a resistor R2, one end of the resistor R1 is electrically connected with the end 12V, the other end of the resistor R1 is electrically connected with one end of the resistor R2, the other end of the resistor R2 is grounded, the resistor R2 is electrically connected with the end 3 of the voltage comparison chip U2A, the end 3 of the voltage comparison chip U2A is electrically connected with one end of a capacitor C3, and the other end of the capacitor C3 is grounded.

[0009] Optionally, the hysteresis circuit and the optocoupler isolation circuit comprise an optocoupler chip U1, the model of the optocoupler chip U1 is EL817, one end of the optocoupler chip U1 is electrically connected with the resistor R3 and the resistor R7 respectively, the other end of the resistor R3 is electrically connected with the 3.3V terminal, the other end of the resistor R7 is electrically connected with the Pr_OTP terminal, and the 3 terminal of the optocoupler chip U1 is grounded.

[0010] Optionally, the negative electrode of the diode D2 is electrically connected with the 1 terminal of the optocoupler chip U1, the positive electrode of the diode D2 is electrically connected with the 2 terminal of the optocoupler chip U1, the 2 terminal of the optocoupler chip U1 is grounded, the 1 terminal of the optocoupler chip U1 is electrically connected with one end of the resistor R4, and the other end of the resistor R4 is electrically connected with the OTP terminal.

[0011] Compared with the prior art, the temperature sampling protection circuit with hysteresis of the isolation power supply has the following beneficial effects:

[0012] The temperature sampling protection circuit with hysteresis of the isolation power supply, through the setting of the hysteresis circuit and the optocoupler isolation circuit, when the input signal reaches the set threshold value, the output signal is reversed, and after the input signal leaves the set threshold value, the output signal remains in the reversed state until another threshold value is reached, and the output is reversed again. The other threshold value can be adjusted by the resistor R10. The high and low levels output by the voltage comparison circuit are isolated by the optocoupler, and a high or low level is output and input to the single-chip microcomputer to determine whether the over-temperature protection is performed. BRIEF DESCRIPTION OF DRAWINGS

[0013] Fig. 1 Fig. 1 is a schematic diagram of a temperature sampling circuit, a voltage reference circuit and a voltage comparison circuit of the present application;

[0014] Fig. 2 Fig. 2 is a schematic diagram of a hysteresis circuit and an optocoupler isolation circuit of the present application. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0016] As Figs. 1-2As shown, the utility model provides a technical scheme: a temperature sampling protection circuit with hysteresis of isolated power supply, temperature sampling protection circuit with hysteresis includes: temperature sampling circuit, voltage reference circuit, voltage comparison circuit, hysteresis circuit and photoelectric coupling isolation circuit.

[0017] Voltage comparison circuit includes voltage comparison chip U2A, temperature sampling circuit includes resistance R6 and resistance R8, one end of resistance R6 is connected with 2 end of voltage comparison chip U2A, the other end of resistance R6 is grounded, one end of resistance R8 is connected with 2 end of voltage comparison chip U2A, the other end of resistance R8 is connected with 12V end, 1 end of voltage comparison chip U2A is connected with one end of resistance R5, the other end of resistance R5 is connected with OTP end, resistance R5 is connected with one end of capacitor C4, the other end of capacitor C4 is grounded.

[0018] Voltage reference circuit includes resistance R1 and resistance R2, one end of resistance R1 is connected with 12V end, the other end of resistance R1 is connected with one end of resistance R2, the other end of resistance R2 is grounded, resistance R2 is connected with 3 end of voltage comparison chip U2A, 3 end of voltage comparison chip U2A is connected with one end of capacitor C3, the other end of capacitor C3 is grounded.

[0019] Wherein, hysteresis circuit and photoelectric coupling isolation circuit include photoelectric coupling chip U1, the model of photoelectric coupling chip U1 is EL817, 4 end of photoelectric coupling chip U1 is connected with resistance R3, one end of resistance R7 respectively, the other end of resistance R3 is connected with 3.3V end, the other end of resistance R7 is connected with Pr OTP end, 3 end of photoelectric coupling chip U1 is grounded.Hysteresis circuit and photoelectric coupling isolation circuit still include diode D2 and resistance R10, one end of resistance R10 is connected with 3 end of photoelectric coupling chip U1, the other end of resistance R10 is connected with 1 end of photoelectric coupling chip U1 through diode D1, the negative pole of diode D2 is connected with 1 end of photoelectric coupling chip U1, the positive pole of diode D2 is connected with 2 end of photoelectric coupling chip U1, 2 end of photoelectric coupling chip U1 is grounded, 1 end of photoelectric coupling chip U1 is connected with one end of resistance R4, the other end of resistance R4 is connected with OTP end.

[0020] As one application of the embodiment:

[0021] The function of the temperature sampling circuit is to convert the temperature value into resistance value, to obtain a voltage value through another resistance R8 voltage division, and to give the voltage to the reverse end of the voltage comparison circuit; the function of the voltage reference circuit is to provide a voltage reference source to the same end of the voltage comparison circuit; the function of the voltage comparison circuit is to compare the values of the temperature sampling circuit and the voltage reference circuit, and to output a high or low level; the function of the hysteresis circuit is that when the input signal reaches the set threshold, the output signal is reversed, and after the input signal leaves the set threshold, the output signal remains in the reversed state until another threshold is reached, and the output is reversed again; the other threshold described can be adjusted by the resistance R10; the function of the optocoupler isolation circuit is to isolate the high or low level output by the voltage comparison circuit through the optocoupler, to output a high or low level to the single-chip microcomputer, and to determine whether the over-temperature protection is implemented.

[0022] The above is a detailed description of the utility model in general, but some modifications or improvements can be made on the basis of the utility model, which is obvious to those skilled in the art. Therefore, without departing from the spirit of the utility model, the modifications or improvements are within the scope of protection of the utility model.

Claims

1. A temperature sampling protection circuit with hysteresis for an isolated power supply, characterized by: The temperature sampling protection circuit with hysteresis comprises a temperature sampling circuit, a voltage reference circuit, a voltage comparison circuit, a hysteresis circuit and an optocoupler isolation circuit, wherein the hysteresis circuit and the optocoupler isolation circuit comprise a diode D1, a diode D2 and a resistor R10.

2. The temperature sampling protection circuit of claim 1, wherein: The voltage comparison circuit comprises a voltage comparison chip U2A.

3. The temperature sampling protection circuit of claim 2, wherein: The temperature sampling circuit comprises a resistor R6 and a resistor R8, one end of the resistor R6 is electrically connected to the 2 end of the voltage comparison chip U2A, the other end of the resistor R6 is grounded, one end of the resistor R8 is electrically connected to the 2 end of the voltage comparison chip U2A, the other end of the resistor R8 is electrically connected to the 12V end, the 1 end of the voltage comparison chip U2A is electrically connected to one end of a resistor R5, the other end of the resistor R5 is electrically connected to the OTP end, the resistor R5 is electrically connected to one end of a capacitor C4, the other end of the capacitor C4 is grounded.

4. The temperature sampling protection circuit of claim 3, wherein: The voltage reference circuit comprises a resistor R1 and a resistor R2, one end of the resistor R1 is electrically connected to the 12V end, the other end of the resistor R1 is electrically connected to one end of the resistor R2, the other end of the resistor R2 is grounded, the resistor R2 is electrically connected to the 3 end of the voltage comparison chip U2A, the 3 end of the voltage comparison chip U2A is electrically connected to one end of a capacitor C3, the other end of the capacitor C3 is grounded.

5. The temperature sampling protection circuit of claim 1, wherein: The hysteresis circuit and the optocoupler isolation circuit comprise an optocoupler chip U1, the model of the optocoupler chip U1 is EL817, the 4 end of the optocoupler chip U1 is respectively electrically connected to a resistor R3 and one end of a resistor R7, the other end of the resistor R3 is electrically connected to the 3.3V end, the other end of the resistor R7 is electrically connected to the Pr_OTP end, the 3 end of the optocoupler chip U1 is grounded.

6. A temperature sampling protection circuit with hysteresis for an isolated power supply according to claim 5, characterized in that: The negative electrode of the diode D2 is electrically connected to the 1 end of the optocoupler chip U1, the positive electrode of the diode D2 is electrically connected to the 2 end of the optocoupler chip U1, the 2 end of the optocoupler chip U1 is grounded, the 1 end of the optocoupler chip U1 is electrically connected to one end of a resistor R4, the other end of the resistor R4 is electrically connected to the OTP end, one end of the resistor R10 is electrically connected to the 3 end of the optocoupler chip U1, the other end of the resistor R10 is electrically connected to the 1 end of the optocoupler chip U1 through the diode D1.

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