CN210166432U - Low-voltage low-frequency small-signal current detection circuit - Google Patents
Low-voltage low-frequency small-signal current detection circuit Download PDFInfo
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- CN210166432U CN210166432U CN201920642517.9U CN201920642517U CN210166432U CN 210166432 U CN210166432 U CN 210166432U CN 201920642517 U CN201920642517 U CN 201920642517U CN 210166432 U CN210166432 U CN 210166432U
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- 238000001514 detection method Methods 0.000 title claims abstract description 37
- 239000003990 capacitor Substances 0.000 claims abstract description 69
- 230000008878 coupling Effects 0.000 claims description 9
- 238000010168 coupling process Methods 0.000 claims description 9
- 238000005859 coupling reaction Methods 0.000 claims description 9
- 238000004146 energy storage Methods 0.000 claims description 5
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- 238000010586 diagram Methods 0.000 description 6
- 238000012986 modification Methods 0.000 description 5
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- 238000005070 sampling Methods 0.000 description 5
- 238000004088 simulation Methods 0.000 description 4
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- 238000004378 air conditioning Methods 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
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Abstract
The utility model provides a low-voltage low-frequency small-signal current detection circuit, wherein one end of a first capacitor is connected with a current input end and one end of a ninth resistor; the other end of the first capacitor is connected with one ends of the second resistor and the third resistor, and the other end of the second resistor is connected with one end of the first resistor, a collector and a base of the first NPN triode; the other end of the third resistor is connected with a base electrode of the second NPN triode and one end of the second capacitor; a collector of the second NPN triode is connected with one end of the sixth resistor and one end of the seventh resistor, an emitter of the second NPN triode is connected with one end of the fifth resistor and one end of the fourth resistor, and the other end of the fourth resistor is connected with one end of the fourth capacitor; the power supply is connected with the other ends of the first resistor and the sixth resistor and the emitting electrode of the PNP triode, the other end of the seventh resistor is connected with the base electrode of the PNP triode, and the emitting electrode of the PNP triode is connected with one end of the eighth resistor, one end of the third capacitor and the microprocessor; the other terminals are all grounded. The utility model has the advantages of with low costs, the reliability is high, sensitivity is high, parameter design is nimble.
Description
Technical Field
The utility model relates to an electricity field, concretely relates to low pressure low frequency small signal current detection circuit.
Background
For low-voltage low-frequency small-signal current, the following three detection methods are commonly used at present:
(1) the sampling resistor is connected in series, and the voltage on the resistor is amplified through a triode. The method has the advantages of low cost, small volume and the like, and has wide application range. However, the triode amplification is easy to cause distortion, and is greatly influenced by temperature, so that the sampling precision and sensitivity are influenced.
(2) And an operational amplifier mode is adopted for current detection. However, the offset voltage of the common operational amplifier is relatively large, and the high-precision operational amplifier will increase the cost. The use of operational amplifiers also causes common mode interference, which requires design considerations to distinguish between useful small signal currents and common mode noise currents.
(3) A current sensor is used. The current sensor has high precision and good performance. But the cost of current sensors is high. Some current sensors are large in size, need power supply, and are limited in application to high-density Printed Circuit Boards (PCBs).
SUMMERY OF THE UTILITY MODEL
The to-be-solved technical problem of the utility model is how to improve low pressure low frequency small signal current detection's precision, sensitivity and reliability, reduce its cost simultaneously.
In order to solve the technical problem, the technical scheme of the utility model is to provide a low pressure low frequency small signal current detection circuit, its characterized in that: the circuit comprises a first capacitor, wherein one end of the first capacitor is connected with a current input end and one end of a ninth resistor, and the other end of the ninth resistor is grounded; the other end of the first capacitor is connected with one end of a second resistor and one end of a third resistor, the other end of the second resistor is connected with one end of a first resistor, a collector of a first NPN triode and a base of the first NPN triode, and an emitter of the first NPN triode is grounded; the other end of the third resistor is connected with a base electrode of the second NPN triode and one end of a second capacitor, and the other end of the second capacitor is grounded; a collector of the second NPN triode is connected with one end of a sixth resistor and one end of a seventh resistor, an emitter of the second NPN triode is connected with one end of a fifth resistor and one end of a fourth resistor, the other end of the fifth resistor is grounded, the other end of the fourth resistor is connected with one end of a fourth capacitor, and the other end of the fourth capacitor is grounded; the power supply is connected with the other end of the first resistor, the other end of the sixth resistor and an emitting electrode of the PNP triode, the other end of the seventh resistor is connected with a base electrode of the PNP triode, the emitting electrode of the PNP triode is connected with one end of an eighth resistor, one end of a third capacitor and a current output end, and the current output end is connected with the microprocessor; the other end of the eighth resistor is grounded, and the other end of the third capacitor is grounded.
Preferably, the first NPN transistor and the second NPN transistor are of the same type.
Preferably, the first capacitor is a dc blocking coupling capacitor.
Preferably, the second capacitor is a filter capacitor.
Preferably, the third capacitor is an energy storage capacitor.
Preferably, the fourth capacitor is a filter capacitor.
Preferably, the output end of the current detection circuit is connected with a general I/O port of the microprocessor.
Preferably, the power supply is a 5V dc power supply.
The utility model provides an among the low pressure low frequency small signal current detection circuit, first NPN triode, first resistance, second resistance, first electric capacity constitute and separate straight, coupling circuit, provide voltage V + Vipple for the base of first NPN triode, second NPN triode, wherein, V is the DC offset that first NPN triode, first resistance, second resistance provided, Vipple is the frequency voltage volume that first electric capacity comes from the current input end coupling. When the second NPN triode is turned on, the second NPN triode, the fifth resistor and the sixth resistor form a deep saturation circuit, the PNP triode is turned on, and the output end of the current detection circuit is high. The second capacitor is a filter capacitor, and the size of Vriple can be adjusted properly. The third capacitor is an energy storage capacitor, and can charge the eighth resistor to continuously maintain the last level state in a short time. If the current amplitude of the current input end is smaller than a certain value, the base electrodes of the first NPN triode and the second NPN triode are in a cut-off state due to the fact that the maximum value of the voltage V + Vriple is too low, the base electrode of the PNP type triode is in a high level and is also in a cut-off state, and then the output end of the current detection circuit is low.
Compared with the prior art, the utility model provides a low pressure low frequency small signal current detection circuit has following beneficial effect:
1. the cost is reduced by adopting low-cost discrete components;
2. the circuit design is simple, the parameter adjustment is convenient, and the application is convenient;
3. the circuit design has two major components of direct current and frequency components at the same time, and is sensitive to the detection of the frequency components;
4. the symmetrical triode can overcome the problem of temperature drift and enhance the stability and reliability of the circuit.
Drawings
Fig. 1 is a schematic diagram of a low-voltage low-frequency small-signal current detection circuit provided in this embodiment;
FIG. 2 is a diagram of a simulation result of the low-voltage low-frequency small-signal current detection circuit when the current amplitude at the current input terminal is 5 mA;
fig. 3 is a diagram of a simulation result of the low-voltage low-frequency small-signal current detection circuit when the current amplitude of the current input terminal is 30 mA.
Detailed Description
Fig. 1 is a schematic diagram of a low-voltage low-frequency small-signal current detection circuit provided in this embodiment, where the low-voltage low-frequency small-signal current detection circuit includes a first capacitor C1, one end of the first capacitor C1 is connected to a current input end and one end of a ninth resistor R9, and the other end of the ninth resistor R9 is grounded; the other end of the first capacitor C1 is connected with one end of a second resistor R2 and one end of a third resistor R3, the other end of the second resistor R2 is connected with one end of a first resistor R1, a collector of a first NPN triode Q1 and a base of a first NPN triode Q1, and an emitter of the first NPN triode Q1 is grounded; the other end of the third resistor R3 is connected with the base of the second NPN triode Q2 and one end of the second capacitor C2, and the other end of the second capacitor C2 is grounded; a collector of the second NPN triode Q2 is connected to one end of the sixth resistor R6 and one end of the seventh resistor R7, an emitter of the second NPN triode Q2 is connected to one end of the fifth resistor R5 and one end of the fourth resistor R4, the other end of the fifth resistor R5 is grounded, the other end of the fourth resistor R4 is connected to one end of the fourth capacitor C4, and the other end of the fourth capacitor C4 is grounded; the power supply is connected with the other end of the first resistor R1, the other end of the sixth resistor R6 and the emitting electrode of the PNP triode Q3, the other end of the seventh resistor R7 is connected with the base electrode of the PNP triode Q3, the emitting electrode of the PNP triode Q3 is connected with one end of the eighth resistor R8, one end of the third capacitor C3 and the current output end, and the current output end is connected with the microprocessor MCU; the other end of the eighth resistor R8 and the other end of the third capacitor C3 are grounded.
The first NPN triode Q1 and the second NPN triode Q2 are NPN type triodes of the same type, and can inhibit temperature drift and enhance the reliability of the detection circuit. Q3 is a PNP transistor. The first NPN triode Q1, the first resistor R1, the second resistor R2, and the first capacitor C1 constitute a dc blocking and coupling circuit, and provide a voltage V + Vripple to the bases of the first NPN triode Q1 and the second NPN triode Q2, where V is a dc bias provided by the first NPN triode Q1, the first resistor R1, and the second resistor R2, and Vripple is a frequency voltage amount coupled from the current input terminal by the first capacitor C1. When the second NPN triode Q2 is turned on, the second NPN triode Q2, the fifth resistor R5, and the sixth resistor R6 form a deep saturation circuit, and the PNP triode Q3 is turned on, and at this time, the output terminal of the current detection circuit is high. The second capacitor C2 is a filter capacitor, and the size of Vripple can be adjusted properly. The third capacitor C3 is an energy storage capacitor, and can charge the eighth resistor R8 to maintain the previous level state for a short time.
If the current amplitude of the current input end is smaller than a certain value, the base electrodes of the first NPN triode Q1 and the second NPN triode Q2 are in a cut-off state due to the fact that the maximum value of the voltage V + Vriple is too low, the base electrode of the PNP triode Q3 is in a high level and is also in a cut-off state, and then the output end of the current detection circuit is low.
In the embodiment, the working current value of the air suction motor of the automobile electronic air conditioning system is sampled. The air suction motor sucks air in the vehicle and transmits the air to the temperature sensor in the vehicle, so that the sensitivity and the real-time performance of the temperature sensor are enhanced. The current input end is the sampled working current of the air suction motor, and the current output end is connected to a GPIO port (general purpose I/O port) of the MCU.
The first NPN transistor Q1 and the second NPN transistor Q2 are of the SMMBTA06WT1 type by ONSEMI. The PNP transistor Q3 is MMBT3906Q manufactured by ONSEMI corporation.
The ninth resistor R9 is a shunt resistor that converts the sampled current amount into a voltage amount.
The first capacitor C1 is a blocking, coupling capacitor. The second capacitor C2 is a filter capacitor and can adjust the amplitude of Vripple. The third capacitor C3 is an energy storage capacitor. The fourth capacitor C4 is a filter capacitor.
The power supply is a 5V direct current power supply.
In this embodiment, the normal operating current frequency of the suction motor is 330Hz, and the current peak-peak value is 30 mA. The reasonable configuration of the first resistor R1 and the ninth resistor R9 can obtain the dc bias voltage V meeting the detection requirement, and the reasonable selection of the capacitance value of the first capacitor C1 can obtain the reasonable coupling voltage Vripple. Vripple is the amount of voltage at the same frequency as the load current. In the present embodiment, V is 0.4V. When the air suction motor works normally, the maximum value of coupling voltage Vriple is larger than 0.1V, the maximum value of V + Vriple in a current sampling period is larger than 0.5V, the first NPN triode Q1 and the second NPN triode Q2 are opened, the second NPN triode Q2 is in a deep saturation state when the V + Vriple is larger than the opening voltage, the PNP triode Q3 is opened, and the current output end is pulled high. The third capacitor C3 is a storage capacitor that provides a discharge current to maintain the output of the current detection circuit at a high level when V + Vripple is turned off during the current sampling period less than the turn-on voltage of the second NPN transistor Q2 and the PNP transistor Q3 is also turned off.
When the suction motor is blocked or the rotating speed is too slow, the peak-peak value of the current is within 5 mA. The maximum value of the coupling voltage Vriple in the whole current sampling period is less than 0.1V, the maximum value of V + Vriple is less than 0.5V, the first NPN triode Q1 and the second NPN triode Q2 are in a cut-off state, the PNP triode Q3 is also in a cut-off state, and the output end of the current detection circuit is arranged at a low position;
the MCU judges the working state of the air suction motor by reading different levels of the output end of the current detection circuit.
Fig. 2 is a simulation result diagram of the low-voltage low-frequency small-signal current detection circuit provided in this embodiment when the current amplitude at the current input terminal is 5mA, where a solid line is the detection current at the input terminal of the current detection circuit, and a dotted line is the output level at the output terminal of the current detection circuit.
Fig. 3 is a simulation result diagram of the low-voltage low-frequency small-signal current detection circuit provided in this embodiment when the current amplitude at the current input terminal is 30mA, where a solid line is the detection current at the input terminal of the current detection circuit, and a dotted line is the output level at the output terminal of the current detection circuit.
As can be seen from fig. 2 and 3, the low-voltage low-frequency small-signal current detection circuit provided in this embodiment passes the verification in the high-temperature and low-temperature environment, and functions normally.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element may be termed a second element, and, similarly, a second element may be termed a first element, without departing from the scope of example embodiments.
The foregoing is merely a preferred embodiment of the present invention, and is not intended to limit the present invention in any way and in any way, and it should be understood that modifications and additions may be made by those skilled in the art without departing from the method of the present invention, and such modifications and additions are also considered to be within the scope of the present invention. Those skilled in the art can make various changes, modifications and evolutions equivalent to those made by the above-disclosed technical content without departing from the spirit and scope of the present invention, and all such changes, modifications and evolutions are equivalent embodiments of the present invention; meanwhile, any changes, modifications and evolutions of equivalent changes to the above embodiments according to the actual technology of the present invention are also within the scope of the technical solution of the present invention.
Claims (8)
1. A low-voltage low-frequency small-signal current detection circuit is characterized in that: the circuit comprises a first capacitor (C1), wherein one end of the first capacitor (C1) is connected with a current input end and one end of a ninth resistor (R9), and the other end of the ninth resistor (R9) is grounded; the other end of the first capacitor (C1) is connected with one end of a second resistor (R2) and one end of a third resistor (R3), the other end of the second resistor (R2) is connected with one end of a first resistor (R1), a collector of a first NPN triode (Q1) and a base of the first NPN triode (Q1), and an emitter of the first NPN triode (Q1) is grounded; the other end of the third resistor (R3) is connected with the base of a second NPN triode (Q2) and one end of a second capacitor (C2), and the other end of the second capacitor (C2) is grounded; a collector of the second NPN triode (Q2) is connected to one end of a sixth resistor (R6) and one end of a seventh resistor (R7), an emitter of the second NPN triode (Q2) is connected to one end of a fifth resistor (R5) and one end of a fourth resistor (R4), the other end of the fifth resistor (R5) is grounded, the other end of the fourth resistor (R4) is connected to one end of a fourth capacitor (C4), and the other end of the fourth capacitor (C4) is grounded; the power supply is connected with the other end of the first resistor (R1), the other end of the sixth resistor (R6) and the emitter of a PNP triode (Q3), the other end of the seventh resistor (R7) is connected with the base of the PNP triode (Q3), the emitter of the PNP triode (Q3) is connected with one end of an eighth resistor (R8), one end of a third capacitor (C3) and a current output end, and the current output end is connected with a Microprocessor (MCU); the other end of the eighth resistor (R8) is grounded, and the other end of the third capacitor (C3) is grounded.
2. A low voltage low frequency small signal current sense circuit as claimed in claim 1 wherein: the first NPN triode (Q1) and the second NPN triode (Q2) are of the same type.
3. A low voltage low frequency small signal current sense circuit as claimed in claim 1 wherein: the first capacitor (C1) is a DC blocking coupling capacitor.
4. A low voltage low frequency small signal current sense circuit as claimed in claim 1 wherein: the second capacitor (C2) is a filter capacitor.
5. A low voltage low frequency small signal current sense circuit as claimed in claim 1 wherein: the third capacitor (C3) is an energy storage capacitor.
6. A low voltage low frequency small signal current sense circuit as claimed in claim 1 wherein: the fourth capacitor (C4) is a filter capacitor.
7. A low voltage low frequency small signal current sense circuit as claimed in claim 1 wherein: the output end of the current detection circuit is connected with a general I/O port of a Microprocessor (MCU).
8. A low voltage low frequency small signal current sense circuit as claimed in claim 1 wherein: the power supply is a 5V direct current power supply.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201920642517.9U CN210166432U (en) | 2019-05-07 | 2019-05-07 | Low-voltage low-frequency small-signal current detection circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201920642517.9U CN210166432U (en) | 2019-05-07 | 2019-05-07 | Low-voltage low-frequency small-signal current detection circuit |
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| CN210166432U true CN210166432U (en) | 2020-03-20 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110007128A (en) * | 2019-05-07 | 2019-07-12 | 延锋伟世通电子科技（上海）有限公司 | A kind of low pressure low frequency small-signal current detection circuit |
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2019
- 2019-05-07 CN CN201920642517.9U patent/CN210166432U/en not_active Withdrawn - After Issue
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110007128A (en) * | 2019-05-07 | 2019-07-12 | 延锋伟世通电子科技（上海）有限公司 | A kind of low pressure low frequency small-signal current detection circuit |
| CN110007128B (en) * | 2019-05-07 | 2023-11-21 | 延锋伟世通电子科技（上海）有限公司 | Low-voltage low-frequency small-signal current detection circuit |
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