CN110007128A - A kind of low pressure low frequency small-signal current detection circuit - Google Patents
A kind of low pressure low frequency small-signal current detection circuit Download PDFInfo
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- CN110007128A CN110007128A CN201910375831.XA CN201910375831A CN110007128A CN 110007128 A CN110007128 A CN 110007128A CN 201910375831 A CN201910375831 A CN 201910375831A CN 110007128 A CN110007128 A CN 110007128A
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- 238000001514 detection method Methods 0.000 title claims abstract description 39
- 239000003990 capacitor Substances 0.000 claims abstract description 71
- 230000000903 blocking effect Effects 0.000 claims description 5
- 230000035945 sensitivity Effects 0.000 abstract description 4
- 230000005611 electricity Effects 0.000 description 10
- 238000010586 diagram Methods 0.000 description 6
- 238000005070 sampling Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 4
- 238000004088 simulation Methods 0.000 description 4
- 238000013461 design Methods 0.000 description 3
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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Abstract
The present invention provides a kind of low pressure low frequency small-signal current detection circuit, first capacitor one end connects current input terminal and the 9th resistance one end；The first capacitor other end connects second and third resistance one end, and the second resistance other end connects the collector and base stage of first resistor one end, the first NPN triode；The 3rd resistor other end connects base stage and second capacitor one end of the second NPN triode；The collector of second NPN triode connects the six, the seven resistance one end, and the emitter of the second NPN triode connects the five, the four resistance one end, and the 4th resistance other end connects the 4th capacitor one end；Power supply connects the emitter of first, the six resistance other ends and PNP triode, and the 7th resistance other end connects the base stage of PNP triode, and the emitter of PNP triode connects the 8th resistance one end, third capacitor one end and microprocessor；Remaining terminals is grounded.The present invention has the advantages that at low cost, high reliablity, high sensitivity, parameter designing are flexible.
Description
Technical field
The present invention relates to electricity fields, and in particular to a kind of low pressure low frequency small-signal current detection circuit.
Background technique
For low pressure low frequency small-signal current, currently used detection method has following three kinds:
(1) series connection sampling resistor passes through the method that triode amplifies ohmically voltage again.This method is due to low in cost, body
The advantages that product is small is wider with face.But triode amplification be easy to cause distortion, and be affected by temperature it is larger, influence sampling precision with
Sensitivity.
(2) current detecting is made using amplifier mode.But common offset voltage is bigger, and high-operational amplifier then can band
Carry out the increase of cost.And the use of amplifier also brings along common mode interference, needs to consider to distinguish useful small signal in the design
Electric current and common mode noise current.
(3) current sensor is used.Current sensor precision is high, and performance is good.But current sensor high expensive.Some electricity
Flow sensor volume is larger, needs to power, and the application on high-density printed circuit board PCB is also by limitation.
Summary of the invention
The technical problem to be solved by the present invention is to how to improve low pressure low frequency small-signal current detection precision, sensitivity and
Reliability reduces its cost simultaneously.
In order to solve the above-mentioned technical problem, the technical solution of the present invention is to provide a kind of detections of low pressure low frequency small-signal current
Circuit, it is characterised in that: including first capacitor, first capacitor one end connection current input terminal and the 9th resistance one end, institute
State the 9th resistance other end ground connection；First capacitor other end connection second resistance one end and 3rd resistor one end, described the
The two resistance other ends connect first resistor one end, the collector of the first NPN triode and the base stage of first NPN triode,
The emitter of first NPN triode is grounded；The 3rd resistor other end connects the base stage and second of the second NPN triode
Capacitor one end, the second capacitor other end ground connection；The collector of second NPN triode connects the 6th resistance one end and the
Seven resistance one end, the emitter of second NPN triode connect the 5th resistance one end and the 4th resistance one end, the 5th electricity
Other end ground connection is hindered, the 4th resistance other end connects the 4th capacitor one end, the 4th capacitor other end ground connection；Power supply connects
Connect the emitter of the first resistor other end, the 6th the resistance other end and PNP triode, the connection of the 7th resistance other end
The emitter of the base stage of the PNP triode, the PNP triode connects the 8th resistance one end, third capacitor one end and electric current
Output end, the current output terminal connect microprocessor；The 8th resistance other end ground connection, another termination of third capacitor
Ground.
Preferably, first NPN triode and the second NPN triode are same model.
Preferably, the first capacitor is blocking coupled capacitor.
Preferably, second capacitor is filter capacitor.
Preferably, the third capacitor is storage capacitor.
Preferably, the 4th capacitor is filter capacitor.
Preferably, general purpose I/O port of the current detection circuit output end connection microprocessor.
Preferably, the power supply is 5V DC power supply.
In low pressure low frequency small-signal current detection circuit provided by the invention, the first NPN triode, first resistor, second
Resistance, first capacitor form blocking, coupling circuit, provide voltage V+ to the first NPN triode, the base stage of the second NPN triode
Vripple, wherein V be the first NPN triode, first resistor, second resistance provide direct current biasing, Vripple be first electricity
Hold from current input terminal and couples the voltage to frequency amount to come.When the second NPN triode is opened, the second NPN triode, the 5th electricity
Resistance, the 6th resistance form depth saturated circuit, open PNP type triode, and the output end of current detection circuit is height at this time.Second
Capacitor is filter capacitor, can suitably adjust the size of Vripple.Third capacitor is storage capacitor, can be filled to the 8th resistance
Electricity makes it persistently maintain a level state in a short time.If the current amplitude of current input terminal is less than certain numerical value,
First NPN triode, the base stage of the second NPN triode are in off state, PNP since voltage V+Vripple maximum value is too low
The base stage of type triode is high level, is also at off state, then the output end output of current detection circuit is low.
Compared with prior art, low pressure low frequency small-signal current detection circuit provided by the invention has the following beneficial effects:
1, using the discrete component of low cost, cost is reduced；
2, circuit design is simple, and parameter regulation is convenient, convenient for application；
3, circuit design exists simultaneously direct current and the big ingredient of frequency component two, sensitive to the detection of frequency component；
4, the application of symmetrical triode can overcome the problems, such as temperature drift, enhance the stability and reliability of circuit.
Detailed description of the invention
Fig. 1 is the schematic diagram of low pressure low frequency small-signal current detection circuit provided in this embodiment；
Fig. 2 is the simulation result diagram of low pressure low frequency small-signal current detection circuit when current input terminal current amplitude is 5mA；
Fig. 3 is the simulation result diagram of low pressure low frequency small-signal current detection circuit when current input terminal current amplitude is 30mA.
Specific embodiment
Fig. 1 is low pressure low frequency small-signal current detection circuit schematic diagram provided in this embodiment, and the low pressure low frequency is small
Signal code detection circuit includes first capacitor C1, and the one end first capacitor C1 connects current input terminal and the 9th one end resistance R9,
9th resistance R9 other end ground connection；First capacitor C1 other end connection one end second resistance R2 and the one end 3rd resistor R3, second
The resistance R2 other end connects the one end first resistor R1, the collector of the first NPN triode Q1 and the base of the first NPN triode Q1
Pole, the emitter ground connection of the first NPN triode Q1；The 3rd resistor R3 other end connects the base stage and the of the second NPN triode Q2
Two one end capacitor C2, second capacitor C2 other end ground connection；The collector of second NPN triode Q2 connect the 6th one end resistance R6 and
7th one end resistance R7, emitter the 5th one end resistance R5 of connection of the second NPN triode Q2 and the 4th one end resistance R4, the 5th
Resistance R5 other end ground connection, the 4th resistance R4 other end connect the 4th one end capacitor C4, the 4th capacitor C4 other end ground connection；Power supply
The emitter of the first resistor R1 other end, the 6th resistance R6 other end and PNP triode Q3 is connected, the 7th resistance R7 other end connects
The base stage of PNP triode Q3 is connect, the emitter of PNP triode Q3 connects the 8th one end resistance R8, third one end capacitor C3 and electricity
Output end is flowed, current output terminal connects Micro-processor MCV；The 8th resistance R8 other end, third capacitor C3 other end ground connection.
First NPN triode Q1, the second NPN triode Q2 are the NPN type triode with model, and temperature drift can be inhibited to move and increased
The reliability of strong detection circuit.Q3 is PNP type triode.First NPN triode Q1, first resistor R1, second resistance R2, first
Capacitor C1 forms blocking, coupling circuit, provides voltage V+ to the first NPN triode Q1, the base stage of the second NPN triode Q2
Vripple, wherein V is the direct current biasing that the first NPN triode Q1, first resistor R1, second resistance R2 are provided, and Vripple is
First capacitor C1 couples the voltage to frequency amount to come from current input terminal.When the second NPN triode Q2 is opened, the 2nd NPN tri-
Pole pipe Q2, the 5th resistance R5, the 6th resistance R6 form depth saturated circuit, open PNP type triode Q3, at this time current detecting electricity
The output end on road is height.Second capacitor C2 is filter capacitor, can suitably adjust the size of Vripple.Third capacitor C3 is storage
Energy capacitor can make it persistently maintain a level state in a short time to the 8th resistance R8 charging.
If the current amplitude of current input terminal is less than certain numerical value, the first NPN triode Q1, the second NPN triode Q2
Base stage due to voltage V+Vripple maximum value it is too low be in off state, the base stage of PNP type triode Q3 is high level,
In off state, then the output end output of current detection circuit is low.
In the present embodiment, sampling be vehicle electronic air conditioner system induced-draught electric motor working current value.Induced-draught electric motor will
In-vehicle air sucks and is transmitted to vehicle interior temperature sensor, enhances the sensitivity and real-time of temperature sensor.Current input terminal is
It is the induced-draught electric motor operating current of sampling, current output terminal accesses the GPIO mouth (general purpose I/O port) of MCU.
First NPN triode Q1, the second NPN triode Q2 use the SMMBTA06WT1 type of ONSEMI company.Tri- pole PNP
Pipe Q3 uses the MMBT3906Q type of ONSEMI company.
9th resistance R9 is bypass resistance, and the magnitude of current sampled is converted into voltage.
First capacitor C1 is blocking, coupled capacitor.Second capacitor C2 is filter capacitor, and Vripple amplitude is adjusted.Third
Capacitor C3 is storage capacitor.4th capacitor C4 is filter capacitor.
Power supply is 5V DC power supply.
In the present embodiment, induced-draught electric motor running current frequency 330Hz, electric current peak-to-peak value 30mA.Reasonable disposition first
The available DC offset voltage V for meeting testing requirements of resistance R1, the 9th resistance R9 reasonably selects the capacitor of first capacitor C1
It is worth available reasonable coupled voltages Vripple.Vripple is the voltage with load current same frequency.In the present embodiment
In, V is 0.4V.When induced-draught electric motor works normally, coupled voltages Vripple maximum value is greater than 0.1V, and V+Vripple is in electric current
Maximum value is greater than 0.5V in sampling period, and the first NPN triode Q1, the second NPN triode Q2 are opened, the second NPN triode Q2
When V+Vripple is greater than its cut-in voltage, it is in depth saturation state, PNP triode Q3 is opened, and current output terminal is drawn
It is high.Third capacitor C3 is storage capacitor, when V+Vripple is in unlatching electricity of the current sample period less than the second NPN triode Q2
Pressure and closes, while when PNP triode Q3 is also switched off, its offer discharge current maintains the output end of current detection circuit
High level.
When induced-draught electric motor is blocked or revolving speed is excessively slow, electric current peak-to-peak value is in 5mA.Coupled voltages Vripple is in entire electricity
It flows maximum value in the sampling period and is less than 0.1V, V+Vripple maximum value is less than 0.5V, the first NPN triode Q1, the 2nd NPN tri-
Pole pipe Q2 is in off state, and PNP triode Q3 is also at off state, and the output end of current detection circuit is set low；
Level MCU different by the output end for reading current detection circuit, to judge induced-draught electric motor working condition.
Fig. 2 is the low pressure low frequency small-signal current detection provided in this embodiment when current input terminal current amplitude is 5mA
The simulation result diagram of circuit, wherein solid line is the detection electric current of current detection circuit input terminal, and dotted line is that current detection circuit is defeated
The output level of outlet.
Fig. 3 is the low pressure low frequency small-signal current inspection provided in this embodiment when current input terminal current amplitude is 30mA
The simulation result diagram of slowdown monitoring circuit, wherein solid line is the detection electric current of current detection circuit input terminal, and dotted line is current detection circuit
The output level of output end.
By Fig. 2 and Fig. 3 it is found that low pressure low frequency small-signal current detection circuit provided in this embodiment is in high and low temperature environment
By verifying, function is normal.
Although it should be understood that herein may usage amount term " first ", " second " etc. each unit is described,
But these units should not be limited by these terms.The use of these items is only for by a unit and another unit
It distinguishes.For example, without departing substantially from the range of exemplary embodiment, it is single that first unit can be referred to as second
Member, and similarly second unit can be referred to as first unit.
The above, only presently preferred embodiments of the present invention, not to the present invention in any form with substantial limitation,
It should be pointed out that under the premise of not departing from the method for the present invention, can also be made for those skilled in the art
Several improvement and supplement, these are improved and supplement also should be regarded as protection scope of the present invention.All those skilled in the art,
Without departing from the spirit and scope of the present invention, when made using disclosed above technology contents it is a little more
Dynamic, modification and the equivalent variations developed, are equivalent embodiment of the invention；Meanwhile all substantial technologicals pair according to the present invention
The variation, modification and evolution of any equivalent variations made by above-described embodiment, still fall within the range of technical solution of the present invention
It is interior.
Claims (8)
1. a kind of low pressure low frequency small-signal current detection circuit, it is characterised in that: including first capacitor (C1), the first capacitor
(C1) one end connection current input terminal and the 9th one end resistance (R9), the 9th resistance (R9) other end ground connection；Described first
Capacitor (C1) other end connects second resistance one end (R2) and the one end 3rd resistor (R3), and second resistance (R2) other end connects
Meet the base stage of the one end first resistor (R1), the collector of the first NPN triode (Q1) and first NPN triode (Q1), institute
State the emitter ground connection of the first NPN triode (Q1)；3rd resistor (R3) other end connection the second NPN triode (Q2)
Base stage and the one end the second capacitor (C2), the second capacitor (C2) other end ground connection；The current collection of second NPN triode (Q2)
Pole connects the 6th resistance one end (R6) and the 7th one end resistance (R7), the emitter connection of second NPN triode (Q2) the
Five resistance one end (R5) and the 4th one end resistance (R4), the 5th resistance (R5) other end ground connection, the 4th resistance (R4)
The other end connects the 4th one end capacitor (C4), the 4th capacitor (C4) other end ground connection；Power supply connects the first resistor
(R1) emitter of the other end, the 6th resistance (R6) other end and PNP triode (Q3), the 7th resistance (R7) other end connect
The base stage of the PNP triode (Q3) is connect, the emitter of the PNP triode (Q3) connects the 8th one end resistance (R8), third
Capacitor one end (C3) and current output terminal, the current output terminal connect microprocessor (MCU)；8th resistance (R8) is another
End ground connection, third capacitor (C3) other end ground connection.
2. a kind of low pressure low frequency small-signal current detection circuit as described in claim 1, it is characterised in that: the first NPN
Triode (Q1) and the second NPN triode (Q2) are same model.
3. a kind of low pressure low frequency small-signal current detection circuit as described in claim 1, it is characterised in that: the first capacitor
It (C1) is blocking coupled capacitor.
4. a kind of low pressure low frequency small-signal current detection circuit as described in claim 1, it is characterised in that: second capacitor
It (C2) is filter capacitor.
5. a kind of low pressure low frequency small-signal current detection circuit as described in claim 1, it is characterised in that: the third capacitor
It (C3) is storage capacitor.
6. a kind of low pressure low frequency small-signal current detection circuit as described in claim 1, it is characterised in that: the 4th capacitor
It (C4) is filter capacitor.
7. a kind of low pressure low frequency small-signal current detection circuit as described in claim 1, it is characterised in that: the current detecting
Circuit output end connects the general purpose I/O port of microprocessor (MCU).
8. a kind of low pressure low frequency small-signal current detection circuit as described in claim 1, it is characterised in that: the power supply is 5V
DC power supply.
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| CN201910375831.XA CN110007128B (en) | 2019-05-07 | 2019-05-07 | Low-voltage low-frequency small-signal current detection circuit |
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| CN201910375831.XA CN110007128B (en) | 2019-05-07 | 2019-05-07 | Low-voltage low-frequency small-signal current detection circuit |
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| CN110007128B CN110007128B (en) | 2023-11-21 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118884025A (en) * | 2024-07-24 | 2024-11-01 | 深圳达德航空科技有限公司 | A current detection circuit |
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