CN212674320U - PTC over-temperature warning circuit - Google Patents
PTC over-temperature warning circuit Download PDFInfo
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- CN212674320U CN212674320U CN202021809023.4U CN202021809023U CN212674320U CN 212674320 U CN212674320 U CN 212674320U CN 202021809023 U CN202021809023 U CN 202021809023U CN 212674320 U CN212674320 U CN 212674320U
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Abstract
The utility model discloses a PTC over-temperature warning circuit, which comprises a PTC, a first input unit, a first comparison unit, a first reference signal unit, a first feedback unit and a photoelectric coupler; the PTC is connected with a voltage source and a first input unit; the first comparison unit is respectively connected with the first input unit, the first reference signal unit and the photoelectric coupler; the first feedback unit is respectively connected with the first comparison unit and the first input unit. The embodiment of the utility model provides an in, when the temperature that PTC detected dropped to the temperature threshold value, photoelectric coupler's signal can not jump immediately (by closing → switch on promptly), but need when the temperature that PTC detected continues to descend along the temperature threshold value, just can trigger photoelectric coupler's signal and jump to make alarm signal (the signal that sends when photoelectric coupler closes promptly) more stable, avoided because PTC's temperature when temperature threshold value is close small undulant, caused alarm signal shake back and forth.
Description
Technical Field
The utility model relates to a PTC fault detection technical field especially relates to a PTC over-temperature warning circuit.
Background
In an industrial control system, a PTC (Positive Temperature Coefficient Temperature sensor) over-Temperature alarm circuit mainly has the functions of: when the temperature detected by the PTC exceeds a preset temperature threshold value (corresponding to the PTC fixed resistance value), the output level is turned over, and the purpose of over-temperature alarm is achieved. At present, the commonly used PTC over-temperature alarm method is as follows: the PTC is connected in series with the primary side of the optocoupler, different current signals are obtained through different resistance values, and the current signals are transmitted to the secondary side through the optocoupler. A disadvantage of this solution is that the alarm signal is prone to jitter, i.e. when the temperature of the PTC fluctuates slightly around the temperature threshold, the alarm signal may be caused to jitter back and forth.
SUMMERY OF THE UTILITY MODEL
The embodiment of the utility model provides a problem that aims at solving current PTC excess temperature warning circuit's warning signal jitter back and forth easily.
In a first aspect, an embodiment of the present invention provides a PTC over-temperature warning circuit, where the PTC over-temperature warning circuit includes a PTC, a first input unit, a first comparison unit, a first reference signal unit, a first feedback unit, and a photoelectric coupler; the PTC is connected with a voltage source and the first input unit; the first comparison unit is respectively connected with the first input unit, the first reference signal unit and the photoelectric coupler; the first feedback unit is respectively connected with the first comparison unit and the first input unit; wherein the detection voltage input to the first comparison unit by the first input unit decreases/increases as the resistance value of the PTC increases/decreases; the first comparison unit turns off/on the photoelectric coupler when the detection voltage input by the first comparison unit is smaller than/larger than the reference voltage input by the first reference signal unit; the first feedback unit reduces a detection voltage of the first input unit when the first comparing unit turns off the photo-coupler.
The further technical scheme is that the first input unit comprises a first resistor and a second resistor; the first end of the first resistor is connected with the voltage source, and the second end of the first resistor is respectively connected with the first end of the second resistor and the first comparison unit; the second end of the second resistor is connected with the first feedback unit, and the PTC is respectively connected with the first end of the first resistor and the second end of the second resistor.
The further technical scheme is that the first comparison unit comprises a third resistor, a first PNP triode and a second PNP triode; a first end of the third resistor is connected with the voltage source, and a second end of the third resistor is respectively connected with an emitter of the first PNP triode and an emitter of the second PNP triode; the base electrode of the first PNP triode is connected with the second end of the first resistor, and the collector electrode of the first PNP triode is connected with the first feedback unit; the base electrode of the second PNP triode is connected with the first reference signal unit, and the collector electrode of the second PNP triode is connected with the photoelectric coupler.
The further technical scheme is that the first feedback unit comprises an NPN triode, a first voltage stabilizing diode, a fourth resistor and a fifth resistor; a collector of the NPN triode is connected with a second end of the second resistor, a base of the NPN triode is connected with a negative electrode of the first voltage stabilizing diode, and an emitter of the NPN triode is grounded through the fourth resistor; the first end of the fifth resistor is connected with the anode of the first voltage-stabilizing diode and the collector of the first PNP triode respectively, and the second end of the fifth resistor is grounded.
The further technical scheme is that the first reference signal unit comprises a sixth resistor and a seventh resistor; the first end of the sixth resistor is connected with the voltage source, and the second end of the sixth resistor is connected with the base electrode of the second PNP triode; and a first end of the seventh resistor is connected with a second end of the sixth resistor, and a second end of the seventh resistor is connected with a cathode of the first voltage stabilizing diode.
Compared with the prior art, the embodiment of the utility model provides a technical effect that can reach includes:
the embodiment of the utility model provides an in, first feedback unit is used for first comparison unit closes during photoelectric coupler, reduce first input unit's detection voltage. Assuming that the detection voltage of the first input unit is a voltage threshold value U1 when the resistance value of the PTC is a resistance value threshold value; the first feedback unit further reduces the detection voltage of the first input unit, so that when the resistance value of the PTC is reduced to the resistance value threshold, the detection voltage of the first input unit cannot rise to the voltage threshold U1, and at this time, the detection voltage input by the first input unit is smaller than the reference voltage input by the first reference signal unit, and the photoelectric coupler is still in a closed state. Only when the resistance value of the PTC continues to decrease, the detection voltage of the first input unit is allowed to rise to the voltage threshold value U1, and the photocoupler is turned on.
It is thus clear that in the embodiment of the utility model provides an in, when the temperature that PTC detected dropped to the temperature threshold value, optoelectronic coupler's signal can not jump immediately (being by closing → switch on), but need be when the temperature that PTC detected continues to descend along the temperature threshold value, just can trigger optoelectronic coupler's signal and jump to make alarm signal (the signal that sends when optoelectronic coupler closes promptly) more stable, avoided because PTC's temperature when temperature threshold value is close small undulant, caused alarm signal shake back and forth.
In a second aspect, an embodiment of the present invention provides a PTC over-temperature warning circuit, where the PTC over-temperature warning circuit includes a PTC, a second input unit, a second comparison unit, a second reference signal unit, a second feedback unit, and a photoelectric coupler; the PTC is connected with the second input unit and grounded, and the second input unit is connected with a voltage source; the second comparison unit is respectively connected with the second input unit, the second reference signal unit and the photoelectric coupler; the second feedback unit is respectively connected with the second comparison unit and the second input unit; wherein the detection voltage input to the second comparison unit by the second input unit increases/decreases as the resistance value of the PTC increases/decreases; the second comparison unit turns off/on the photoelectric coupler when the detection voltage input by the second comparison unit is smaller than/larger than the reference voltage input by the second reference signal unit; the second feedback unit raises the detection voltage of the second input unit when the second comparison unit turns on the photoelectric coupler.
The further technical scheme is that the second input unit comprises an eighth resistor and a ninth resistor; a first end of the eighth resistor is connected with the voltage source, and a second end of the eighth resistor is respectively connected with a first end of the ninth resistor and the second comparing unit; the second end of the ninth resistor is connected with the PTC.
The second comparison unit comprises a tenth resistor, a third PNP triode and a fourth PNP triode; a first end of the tenth resistor is connected with the voltage source, and a second end of the tenth resistor is respectively connected with an emitter of the third PNP triode and an emitter of the fourth PNP triode; a base electrode of the third PNP triode is connected to the second end of the eighth resistor, and a collector electrode of the third PNP triode is connected to the second feedback unit; and the base electrode of the fourth PNP triode is connected with the second reference signal unit, and the collector electrode of the fourth PNP triode is connected with the photoelectric coupler.
The further technical scheme is that the second feedback unit comprises a fifth PNP triode, a second voltage stabilizing diode, an eleventh resistor and a twelfth resistor; a first end of the eleventh resistor is connected with the voltage source, and a second end of the eleventh resistor is connected with an emitter of the fifth PNP triode; the base electrode of the fifth PNP triode is connected with the negative electrode of the second voltage-stabilizing diode, and the collector electrode of the fifth PNP triode is connected with the second end of the ninth resistor; and the first end of the twelfth resistor is respectively connected with the anode of the second voltage-stabilizing diode and the collector of the third PNP triode, and the second end of the twelfth resistor is grounded.
According to a further technical scheme, the second reference signal unit comprises a thirteenth resistor and a fourteenth resistor; a first end of the thirteenth resistor is connected with the voltage source, and a second end of the thirteenth resistor is respectively connected with a base electrode of the fourth PNP triode and a first end of the fourteenth resistor; a second terminal of the fourteenth resistor is connected to ground.
Compared with the prior art, the embodiment of the utility model provides a technical effect that can reach includes:
in the embodiment of the present invention, the second feedback unit is used for the second comparing unit to switch on the photoelectric coupler and then rise the detection voltage of the second input unit. Assuming that the detection voltage of the second input unit is a voltage threshold value U2 when the resistance value of the PTC is a resistance value threshold value; the second feedback unit further increases the detection voltage of the second input unit, so that when the resistance value of the PTC decreases to the resistance value threshold, the detection voltage of the second input unit cannot decrease to the voltage threshold U2, and at this time, the detection voltage input by the second input unit is greater than the reference voltage input by the second reference signal unit, and the photocoupler is still in a conducting state. Only when the resistance value of the PTC continues to decrease, the detection voltage of the second input unit is caused to fall to the voltage threshold value U2, and the photocoupler is turned off.
It is thus clear that in the embodiment of the utility model provides an in, when the temperature that PTC detected dropped to the temperature threshold value, optoelectronic coupler's signal can not jump immediately (by switching on → closing promptly), but need be when the temperature that PTC detected continues to descend along the temperature threshold value, just can trigger optoelectronic coupler's signal and jump to make alarm signal (the signal that sends when optoelectronic coupler switches on promptly) more stable, avoided because PTC's temperature when temperature threshold value is near small undulant, caused alarm signal shake back and forth.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without any creative effort.
Fig. 1 is a schematic structural diagram of a PTC over-temperature warning circuit according to an embodiment of the present invention;
fig. 2 is a circuit of a PTC over-temperature warning circuit according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a PTC over-temperature warning circuit according to another embodiment of the present invention;
fig. 4 is a circuit of a PTC over-temperature warning circuit according to another embodiment of the present invention.
Reference numerals
A PTC1, a first input unit 2, a first comparison unit 3, a first reference signal unit 4, a first feedback unit 5, a photo coupler 6, a second input unit 7, a second comparison unit 8, a second reference signal unit 9, a second feedback unit 10, and a voltage source 100.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, wherein like component numbers represent like components. It is obvious that the embodiments to be described below are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the embodiments of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments of the invention. As used in the description of the embodiments of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
Referring to fig. 1-2, an embodiment of the present invention provides a PTC over-temperature alarm circuit. The PTC over-temperature warning circuit includes a PTC1, a first input unit 2, a first comparison unit 3, a first reference signal unit 4, a first feedback unit 5, and a photo-coupler 6.
In this embodiment, the PTC1 is connected to a voltage source 100 and to the first input unit 2; the first comparing unit 3 is connected to the first input unit 2, the first reference signal unit 4, and the photocoupler 6, respectively; the first feedback unit 5 is connected to the first comparing unit 3 and the first input unit 2, respectively.
The first input unit 2 is used for inputting a detection voltage to the first comparison unit 3, and the detection voltage input by the first input unit 2 is reduced/increased as the resistance value of the PTC1 is increased/reduced; that is, when the resistance value of the PTC1 increases, the detection voltage input by the first input unit 2 decreases; when the resistance value of the PTC1 decreases, the detection voltage input from the first input unit 2 increases.
The first reference signal unit 4 is used for inputting a reference voltage to the first comparing unit 3.
The first comparing unit 3 is configured to compare the detection voltage input by the first input unit 2 with the reference voltage input by the first comparing unit 3, and turn off/on the photocoupler 6 when the detection voltage input by the first input unit 2 is smaller than/larger than the reference voltage input by the first reference signal unit 4.
That is, when the detection voltage inputted from the first input unit 2 is greater than the reference voltage inputted from the first reference signal unit 4, the photocoupler 6 is turned on.
When the detected voltage input by the first input unit 2 is greater than the reference voltage input by the first reference signal unit 4, the resistance value of the PTC1 is less than the set resistance value threshold (i.e. the temperature detected by the PTC1 is lower than the preset temperature threshold), and at this time, the photocoupler 6 is turned on to inform the user that the temperature of the PTC1 is normal.
Further, when the detection voltage input by the first input unit 2 is less than the reference voltage input by the first reference signal unit 4, the photocoupler 6 is turned off.
When the detection voltage input by the first input unit 2 is less than the reference voltage input by the first reference signal unit 4, the resistance value of the PTC1 is greater than the set resistance value threshold (i.e. the temperature detected by the PTC1 exceeds the preset temperature threshold), at this time, the photocoupler 6 is turned off, and the photocoupler 6 sends an alarm signal to inform the user that the temperature of the PTC1 is abnormal.
In the embodiment of the present invention, the first feedback unit 5 is used for reducing the detection voltage of the first input unit 2 when the first comparison unit 3 is closed the photoelectric coupler 6. Assuming that the detection voltage of the first input unit 2 is a voltage threshold U1 when the resistance value of the PTC1 is a resistance value threshold; since the first feedback unit 5 further reduces the detection voltage of the first input unit 2, when the resistance value of the PTC1 is reduced to the resistance value threshold value, the detection voltage of the first input unit 2 cannot be increased to the voltage threshold value U1, and at this time, the detection voltage input by the first input unit 2 is smaller than the reference voltage input by the first reference signal unit 4, and the photocoupler 6 is still in the off state. Only when the resistance of the PTC1 continues to decrease, the detection voltage of the first input unit 2 is allowed to rise to the voltage threshold U1, and the photocoupler 6 is turned on.
It can be seen that, in the embodiment of the present invention, when the temperature detected by PTC1 drops to the temperature threshold, the signal of photoelectric coupler 6 does not jump immediately (i.e. by closing → conducting), but the temperature detected by PTC1 needs to continue to drop along the temperature threshold, and the signal of photoelectric coupler 6 is triggered to jump, so that the alarm signal (i.e. the signal sent when photoelectric coupler 6 is closed) is more stable, and the situation that the alarm signal shakes back and forth due to the small fluctuation of the temperature of PTC1 near the temperature threshold is avoided.
Referring to fig. 2, in some embodiments, for example, the first input unit 2 includes a first resistor R1 and a second resistor R2; a first terminal 11 of the first resistor R1 is connected to the voltage source 100, and a second terminal 12 of the first resistor R1 is connected to the first terminal 21 of the second resistor R2 and the first comparing unit 3, respectively; the second terminal 22 of the second resistor R2 is connected to the first feedback unit 5, and the PTC1 is connected to the first terminal 11 of the first resistor R1 and the second terminal 22 of the second resistor R2, respectively.
Further, the first comparing unit 3 includes a third resistor R3, a first PNP transistor Q1, and a second PNP transistor Q2; a first terminal 31 of the third resistor R3 is connected to the voltage source 100, and a second terminal 32 of the third resistor R3 is connected to the emitter of the first PNP transistor Q1 and the emitter of the second PNP transistor Q2, respectively; the base of the first PNP transistor Q1 is connected to the second end 12 of the first resistor R1, and the collector of the first PNP transistor Q1 is connected to the first feedback unit 5; the base of the second PNP transistor Q2 is connected to the first reference signal unit 4, and the collector of the second PNP transistor Q2 is connected to the photocoupler 6.
Further, the first feedback unit 5 includes an NPN transistor Q3, a first zener diode ZD1, a fourth resistor R4, and a fifth resistor R5; a collector of the NPN transistor Q3 is connected to the second end 22 of the second resistor R2, a base of the NPN transistor Q3 is connected to a negative electrode of the first zener diode ZD1, and an emitter of the NPN transistor Q3 is grounded through the fourth resistor R4; a first end 51 of the fifth resistor R5 is connected to the anode of the first zener diode ZD1 and the collector of the first PNP transistor Q1, respectively, and a second end 52 of the fifth resistor R5 is grounded.
Further, the first reference signal unit 4 includes a sixth resistor R6 and a seventh resistor R7; a first end 61 of the sixth resistor R6 is connected to the voltage source 100, and a second end 62 of the sixth resistor R6 is connected to the base of the second PNP transistor Q2; a first end 71 of the seventh resistor R7 is connected to the second end 62 of the sixth resistor R6, and a second end 72 of the seventh resistor R7 is connected to the cathode of the first zener diode ZD 1.
Referring to fig. 2, the circuit diagram of the PTC over-temperature warning circuit provided in the embodiment of the present invention is now combined to explain the working principle of the PTC over-temperature warning circuit:
at normal temperature, the resistance of the PTC1 is low, the voltage of the base of the first PNP transistor Q1 is greater than the voltage of the base of the second PNP transistor Q2, at this time, the second PNP transistor Q2 is turned on, and the photoelectric coupler 6 is turned on to send a normal signal.
When the PTC1 rises to the temperature threshold, the voltage (voltage threshold U1) of the base of the first PNP transistor Q1 is lower than the voltage of the base of the second PNP transistor Q2, and at this time, the first PNP transistor Q1 is turned on, and the photocoupler 6 is turned off to send out an alarm signal.
Since the first PNP transistor Q1 is turned on, the voltage of the fifth resistor R5 increases, and thus the voltage of the negative electrode of the first zener diode ZD1 increases, that is, the base voltage of the NPN transistor Q3 increases. The increase in voltage at the base of NPN transistor Q3 will cause a current at the collector of NPN transistor Q3 to increase. Further, the current at the collector of the NPN transistor Q3 rises, causing the voltage at the base of the first PNP transistor Q1 to drop further.
Referring to fig. 3 to 4, an embodiment of the present invention provides a PTC over-temperature warning circuit, which includes a PTC1, a second input unit 7, a second comparison unit 8, a second reference signal unit 9, a second feedback unit 10, and a photocoupler 6.
In this embodiment, the PTC1 is connected to the second input unit 7 and grounded, and the second input unit 7 is connected to the voltage source 100. The second comparing unit 8 is respectively connected with the second input unit 7, the second reference signal unit 9 and the photoelectric coupler 6; the second feedback unit 10 is connected to the second comparing unit 8 and the second input unit 7, respectively.
The second input unit 7 is used for inputting a detection voltage to the second comparison unit 8, and the detection voltage input by the second input unit 7 increases/decreases as the resistance value of the PTC1 increases/decreases; that is, when the resistance of the PTC1 increases, the detection voltage input by the second input unit 7 also increases; when the resistance of the PTC1 decreases, the detection voltage inputted from the second input unit 7 also decreases.
The second reference signal unit 9 is used for inputting a reference voltage to the first comparing unit 3.
The second comparing unit 8 is configured to compare the detection voltage input by the second input unit 7 with the reference voltage input by the second comparing unit 8, and turn off/on the photocoupler 6 when the detection voltage input by the second comparing unit 8 is smaller than/larger than the reference voltage input by the second reference signal unit 9.
That is, the photo coupler 6 is turned off when the detection voltage inputted from the second comparing unit 8 is less than the reference voltage inputted from the second reference signal unit 9.
When the detected voltage input by the second input unit 7 is less than the reference voltage input by the second reference signal unit 9, the resistance value of the PTC1 is less than the set resistance value threshold (i.e. the temperature detected by the PTC1 is less than the preset temperature threshold), and at this time, the photocoupler 6 is turned off to inform the user that the temperature of the PTC1 is normal.
Further, when the detection voltage inputted from the second comparing unit 8 is greater than the reference voltage inputted from the second reference signal unit 9, the photo coupler 6 is turned on.
When the detection voltage input by the second comparing unit 8 is greater than the reference voltage input by the second reference signal unit 9, the resistance value of the PTC1 is greater than the set resistance value threshold (that is, the temperature detected by the PTC1 exceeds the preset temperature threshold), at this time, the photocoupler 6 is turned on, and the photocoupler 6 sends an alarm signal to inform the user that the PTC1 is abnormal in temperature.
In the embodiment of the present invention, the second feedback unit 10 is used for the second comparing unit 8 to switch on the photoelectric coupler 6 and then the detection voltage of the second input unit 7 is increased. Assuming that the detection voltage of the second input unit 7 is the voltage threshold U2 when the resistance value of the PTC1 is the resistance value threshold; since the second feedback unit 10 further increases the detection voltage of the second input unit 7, when the resistance value of the PTC1 decreases to the resistance value threshold, the detection voltage of the second input unit 7 cannot decrease to the voltage threshold U2, and at this time, the detection voltage input by the second input unit 7 is greater than the reference voltage input by the second reference signal unit 9, and the photocoupler 6 is still in a conducting state. Only when the resistance value of the PTC1 continues to decrease, the detection voltage of the second input unit 7 is caused to drop to the voltage threshold U2, and the photocoupler 6 is turned off.
It can be seen that, in the embodiment of the present invention, when the temperature detected by PTC1 drops to the temperature threshold, the signal of photoelectric coupler 6 does not jump immediately (i.e. by switching on → closing), but the temperature detected by PTC1 needs to continue to drop along the temperature threshold, and the signal of photoelectric coupler 6 is triggered to jump, so that the alarm signal (i.e. the signal sent when photoelectric coupler 6 is switched on) is more stable, and the alarm signal is prevented from shaking back and forth due to the small fluctuation of the temperature of PTC1 near the temperature threshold.
Referring to fig. 4, the second input unit 7 includes an eighth resistor R8 and a ninth resistor R9; a first end 81 of the eighth resistor R8 is connected to the voltage source 100, and a second end 82 of the eighth resistor R8 is connected to a first end 91 of the ninth resistor R9 and the second comparing unit 8, respectively; the second end 92 of the ninth resistor R9 is connected to the PTC 1.
Further, the second comparing unit 8 includes a tenth resistor R10, a third PNP transistor Q4, and a fourth PNP transistor Q5; a first terminal 101 of the tenth resistor R10 is connected to the voltage source 100, and a second terminal 102 of the tenth resistor R10 is connected to the emitter of the third PNP transistor Q4 and the emitter of the fourth PNP transistor Q5, respectively; the base of the third PNP transistor Q4 is connected to the second terminal 82 of the eighth resistor R8, and the collector of the third PNP transistor Q4 is connected to the second feedback unit 10; the base of the fourth PNP transistor Q5 is connected to the second reference signal unit 9, and the collector of the fourth PNP transistor Q5 is connected to the photocoupler 6.
Further, the second feedback unit 10 includes a fifth PNP transistor Q6, a second zener diode ZD2, an eleventh resistor R11, and a twelfth resistor R12; a first end 111 of the eleventh resistor R11 is connected to the voltage source 100, and a second end 112 of the eleventh resistor R11 is connected to an emitter of the fifth PNP transistor Q6; the base of the fifth PNP transistor Q6 is connected to the cathode of the second zener diode ZD2, and the collector of the fifth PNP transistor Q6 is connected to the second end 92 of the ninth resistor R9; a first end 121 of the twelfth resistor R12 is connected to the anode of the second zener diode ZD2 and the collector of the third PNP transistor Q4, respectively, and a second end 122 of the twelfth resistor R12 is grounded.
Further, the second reference signal unit 9 includes a thirteenth resistor R13 and a fourteenth resistor R14; a first end 131 of the thirteenth resistor R13 is connected to the voltage source 100, and a second end 132 of the thirteenth resistor R13 is connected to the base of the fourth PNP transistor Q5 and the first end 141 of the fourteenth resistor R14, respectively; the second end 142 of the fourteenth resistor R14 is grounded.
Referring to fig. 4, the circuit diagram of the PTC over-temperature warning circuit provided in the embodiment of the present invention is now combined to explain the working principle of the PTC over-temperature warning circuit:
at normal temperature, the resistance of the PTC1 is low, the voltage of the base of the third PNP transistor Q4 is lower than the voltage of the base of the fourth PNP transistor Q5, at this time, the third PNP transistor Q4 is turned on, the fourth PNP transistor Q5 is turned off, and the photoelectric coupler 6 is turned off to send a normal signal.
When the PTC1 rises to the temperature threshold, the voltage (voltage threshold U2) of the base of the third PNP transistor Q4 is greater than the voltage of the base of the fourth PNP transistor Q5, at this time, the third PNP transistor Q4 is turned off, the fourth PNP transistor Q5 is turned on, and the photocoupler 6 is turned on to send out an alarm signal.
Since the third PNP transistor Q4 is turned off, the voltage of the twelfth resistor R12 decreases, and thus the voltage of the cathode of the second zener diode ZD2 decreases, that is, the voltage of the base of the fifth PNP transistor Q6 decreases. Further, the voltage of the collector of the fifth PNP transistor Q6 rises, so that the voltage of the base of the third PNP transistor Q4 further rises.
In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Thus, while the invention has been described with respect to certain embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.
The above description is for the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope of the present invention, and these modifications or replacements should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A PTC over-temperature warning circuit is characterized by comprising a PTC, a first input unit, a first comparison unit, a first reference signal unit, a first feedback unit and a photoelectric coupler; the PTC is connected with a voltage source and the first input unit; the first comparison unit is respectively connected with the first input unit, the first reference signal unit and the photoelectric coupler; the first feedback unit is respectively connected with the first comparison unit and the first input unit; wherein the detection voltage input to the first comparison unit by the first input unit decreases/increases as the resistance value of the PTC increases/decreases; the first comparison unit turns off/on the photoelectric coupler when the detection voltage input by the first comparison unit is smaller than/larger than the reference voltage input by the first reference signal unit; the first feedback unit reduces a detection voltage of the first input unit when the first comparing unit turns off the photo-coupler.
2. The PTC overheat warning circuit according to claim 1, wherein the first input unit includes a first resistor and a second resistor; the first end of the first resistor is connected with the voltage source, and the second end of the first resistor is respectively connected with the first end of the second resistor and the first comparison unit; the second end of the second resistor is connected with the first feedback unit, and the PTC is respectively connected with the first end of the first resistor and the second end of the second resistor.
3. The PTC overheat warning circuit according to claim 2, wherein the first comparing unit includes a third resistor, a first PNP transistor, and a second PNP transistor; a first end of the third resistor is connected with the voltage source, and a second end of the third resistor is respectively connected with an emitter of the first PNP triode and an emitter of the second PNP triode; the base electrode of the first PNP triode is connected with the second end of the first resistor, and the collector electrode of the first PNP triode is connected with the first feedback unit; the base electrode of the second PNP triode is connected with the first reference signal unit, and the collector electrode of the second PNP triode is connected with the photoelectric coupler.
4. The PTC over-temperature warning circuit according to claim 3, wherein the first feedback unit includes an NPN transistor, a first voltage regulator diode, a fourth resistor, and a fifth resistor; a collector of the NPN triode is connected with a second end of the second resistor, a base of the NPN triode is connected with a negative electrode of the first voltage stabilizing diode, and an emitter of the NPN triode is grounded through the fourth resistor; the first end of the fifth resistor is connected with the anode of the first voltage-stabilizing diode and the collector of the first PNP triode respectively, and the second end of the fifth resistor is grounded.
5. The PTC overheat warning circuit according to claim 4, wherein the first reference signal unit includes a sixth resistor and a seventh resistor; the first end of the sixth resistor is connected with the voltage source, and the second end of the sixth resistor is connected with the base electrode of the second PNP triode; and a first end of the seventh resistor is connected with a second end of the sixth resistor, and a second end of the seventh resistor is connected with a cathode of the first voltage stabilizing diode.
6. A PTC over-temperature warning circuit is characterized by comprising a PTC, a second input unit, a second comparison unit, a second reference signal unit, a second feedback unit and a photoelectric coupler; the PTC is connected with the second input unit and grounded, and the second input unit is connected with a voltage source; the second comparison unit is respectively connected with the second input unit, the second reference signal unit and the photoelectric coupler; the second feedback unit is respectively connected with the second comparison unit and the second input unit; wherein the detection voltage input to the second comparison unit by the second input unit increases/decreases as the resistance value of the PTC increases/decreases; the second comparison unit turns off/on the photoelectric coupler when the detection voltage input by the second comparison unit is smaller than/larger than the reference voltage input by the second reference signal unit; the second feedback unit raises the detection voltage of the second input unit when the second comparison unit turns on the photoelectric coupler.
7. The PTC overheat warning circuit according to claim 6, wherein the second input unit includes an eighth resistor and a ninth resistor; a first end of the eighth resistor is connected with the voltage source, and a second end of the eighth resistor is respectively connected with a first end of the ninth resistor and the second comparing unit; the second end of the ninth resistor is connected with the PTC.
8. The PTC over-temperature warning circuit according to claim 7, wherein the second comparing unit includes a tenth resistor, a third PNP transistor, and a fourth PNP transistor; a first end of the tenth resistor is connected with the voltage source, and a second end of the tenth resistor is respectively connected with an emitter of the third PNP triode and an emitter of the fourth PNP triode; a base electrode of the third PNP triode is connected to the second end of the eighth resistor, and a collector electrode of the third PNP triode is connected to the second feedback unit; and the base electrode of the fourth PNP triode is connected with the second reference signal unit, and the collector electrode of the fourth PNP triode is connected with the photoelectric coupler.
9. The PTC overheat warning circuit according to claim 8, wherein the second feedback unit includes a fifth PNP transistor, a second zener diode, an eleventh resistor, and a twelfth resistor; a first end of the eleventh resistor is connected with the voltage source, and a second end of the eleventh resistor is connected with an emitter of the fifth PNP triode; the base electrode of the fifth PNP triode is connected with the negative electrode of the second voltage-stabilizing diode, and the collector electrode of the fifth PNP triode is connected with the second end of the ninth resistor; and the first end of the twelfth resistor is respectively connected with the anode of the second voltage-stabilizing diode and the collector of the third PNP triode, and the second end of the twelfth resistor is grounded.
10. The PTC overheat warning circuit according to claim 9, wherein the second reference signal unit includes a thirteenth resistance and a fourteenth resistance; a first end of the thirteenth resistor is connected with the voltage source, and a second end of the thirteenth resistor is respectively connected with a base electrode of the fourth PNP triode and a first end of the fourteenth resistor; a second terminal of the fourteenth resistor is connected to ground.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021809023.4U CN212674320U (en) | 2020-08-26 | 2020-08-26 | PTC over-temperature warning circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021809023.4U CN212674320U (en) | 2020-08-26 | 2020-08-26 | PTC over-temperature warning circuit |
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| CN212674320U true CN212674320U (en) | 2021-03-09 |
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| CN202021809023.4U Active CN212674320U (en) | 2020-08-26 | 2020-08-26 | PTC over-temperature warning circuit |
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