CN217787215U

CN217787215U - Current sampling circuit with ultra-dynamic range

Info

Publication number: CN217787215U
Application number: CN202220716332.XU
Authority: CN
Inventors: 王永强; 杨志亮
Original assignee: Dornar Electronics Technology Co ltd
Current assignee: Hangzhou Admittance Electronics Co ltd
Priority date: 2022-03-30
Filing date: 2022-03-30
Publication date: 2022-11-11
Anticipated expiration: 2032-03-30

Abstract

The utility model provides a current sampling circuit of super dynamic range, is including establishing ties first sampling resistor Rs1 and second sampling resistor Rs2 on the circuit that awaits measuring, second sampling resistor Rs 2's resistance is far greater than first sampling resistor Rs1 resistance, the parallelly connected conducting voltage of second sampling resistor Rs2 is the diode D1 of Ud, diode D1's negative pole is connected one section between first sampling resistor Rs1 and second sampling resistor Rs2, and the second sampling resistor Rs2 other end is connected to diode D1's positive pole. Compared with the prior art, the utility model discloses can be when detecting heavy current or undercurrent, but the circuit automatic switch-over selects sampling resistance's resistance, satisfies the demand of large resistance sampling undercurrent and small resistance sampling heavy current, has abandoned the input terminal mode of using mechanical switch or difference, has avoided needing artifical or automatic judgement and switching to and the technical defect of signal interruption for a short time can appear in the switching process, also improved the detection precision of electric current to a certain extent simultaneously.

Description

Current sampling circuit with ultra-dynamic range

Technical Field

The utility model relates to a direct current detects technical field, in particular to current sampling circuit of super dynamic range.

Background

In the field of electrical appliances and industrial control, it is often necessary to detect the load current to determine whether the load is working normally. Also, in an instrument having a current test function, a precise current detection circuit is more required. However, in a control circuit or a detection instrument, a signal processing process is based on a voltage signal, and it is troublesome to detect a current flowing through a certain line directly, and it is a common practice to connect a resistor in series in a current loop to be detected, then detect a voltage across the resistor, and calculate a current according to the voltage, and the resistor is called a current sampling resistor.

FIG. 1 is a schematic diagram of a conventional DC current detection circuit; the traditional detection circuit requires high resistance precision and small temperature coefficient for the requirement of a sampling resistor, and has the following difficulties:

1. because the sampling resistor is connected in series to the circuit to be tested, according to ohm's law, when the current to be tested flows through the resistor, the voltage at two ends of the resistor is in direct proportion to the current. In order to reduce the influence on the performance parameters of the original circuit as much as possible, the voltage drop on the detection resistor is suppressed by adopting a sampling resistor with low resistance as much as possible; because the current to be detected flows through the sampling resistor, the power is consumed, the detection resistor can generate heat to cause resistance value change, and the resistance value of the detection resistor is required to be low;

2. if the resistance of the sampling resistor is too small, the signal voltage converted from the current is too small, and thus the signal voltage is submerged by background noise, or the input offset voltage of the operational amplifier close to the amplified signal is close to the background noise, so that the detection accuracy is reduced. In consideration of signal-to-noise ratio of signal processing, the sampling resistor with large resistance value is adopted as much as possible, so that the converted voltage signal is as large as possible, namely, the signal-to-noise ratio of the generated signal is improved, meanwhile, the proportion of the operation amplifier unregulated voltage which is superposed later is reduced, the subsequent line number processing is facilitated, and the detection precision is fully ensured.

For the above two aspects, the values of the sampling resistors seem to be contradictory, however, when the dynamic range of the measured current signal is not large, the dynamic range can be considered in a compromise manner, and a proper resistance value is selected; when a dynamic range with a large current difference needs to be adapted, for example, in a multimeter, when the current range is 10A, the sampling resistor uses 10 milliohms, and when the current range is 2mA, the resistance value of the sampling resistor is hundreds of ohms, and the difference is nearly tens of thousands of times, so that for different current ranges, a mechanical switch or different input terminals have to be used to directly switch and use different sampling resistors, but the process needs manual or automatic judgment and switching, and short-time signal interruption can occur in the switching process.

SUMMERY OF THE UTILITY MODEL

To prior art defect above, the utility model provides a current sampling circuit of super dynamic range as follows:

the technical scheme of the utility model is realized like this:

the utility model provides a current sampling circuit of super dynamic range, is including establishing ties first sampling resistor Rs1 and second sampling resistor Rs2 on the circuit that awaits measuring, second sampling resistor Rs 2's resistance is far greater than first sampling resistor Rs1 resistance, the parallelly connected conducting voltage of second sampling resistor Rs2 is the diode D1 of Ud, one section between first sampling resistor Rs1 and second sampling resistor Rs2 is connected to diode D1's negative pole, and the second sampling resistor Rs2 other end is connected to diode D1's positive pole, diode D1 still parallelly connected diode D2, and diode D1 negative pole is connected to diode D2's positive pole, and diode D1 is anodal to diode D2's negative pole connection, first sampling resistor Rs1 is connected with the signal conditioner respectively with second sampling resistor Rs2, and the MCU unit is all connected through ADC of the same kind to the signal conditioner.

Preferably, the signal conditioners each include a signal amplifier and a filter, the input end of the signal amplifier is connected with the first sampling resistor Rs1 or the second sampling resistor Rs2, the output end of the signal amplifier is connected with the filter, and the output end of the filter is connected with the input end of the ADC.

Compared with the prior art, the utility model discloses there is following beneficial effect:

the utility model discloses a super dynamic range's electric current sampling circuit, can be when detecting heavy current or undercurrent, but the circuit automatic switch-over selects sampling resistor's resistance, satisfy the demand of large resistance sampling undercurrent and undercurrent sampling heavy current, abandoned and used mechanical switch or different input terminal mode, avoided needing artifical or automatic judgement and switching, and the technical defect of the signal interruption of short-term can appear in the switching process, the detection precision of electric current has also been improved to a certain extent to the while.

Drawings

FIG. 1 is a schematic diagram of a conventional DC current detection circuit;

fig. 2 is a schematic circuit diagram of the current sampling circuit with ultra-dynamic range of the present invention.

Detailed Description

The present invention will be described more fully and clearly with reference to the accompanying drawings, which are incorporated in and constitute a part of this specification.

As shown in fig. 2, a current sampling circuit with ultra-dynamic range includes a first sampling resistor Rs1 and a second sampling resistor Rs2 connected in series to a circuit to be tested, the resistance of the second sampling resistor Rs2 is much greater than that of the first sampling resistor Rs1, and the multiple difference between the two sampling resistors is generally greater than 10 ² -10 ⁴ Doubly, the parallelly connected conducting voltage of second sampling resistance Rs2 is the diode D1 of Ud, and the general value of Ud is 0.65V (if adopt schottky diode, then Ud can reduce to about 0.3V), one section between first sampling resistance Rs1 and second sampling resistance Rs2 is connected to diode D1's negative pole, the second sampling resistance Rs2 other end is connected to diode D1's positive pole, diode D1 still connects diode D2 in parallel, diode D2's positive pole connection diode D1 negative pole, diode D2's negative pole connection diode D1 positive pole, first sampling resistance Rs1 and second sampling resistance Rs2 are connected with the signal conditioner respectively, and two way signal conditioner all connect the MCU unit through ADC of the same way, the signal conditioner all includes signal amplifier and wave filter, signal amplifier mainly is used for the amplification to less voltage signal, the wave filter is used for the system noise signal filtering in the circuit, first sampling resistance Rs1 or second sampling resistance Rs2 are connected to the signal amplifier input, the signal amplifier output connects the wave filter, the ADC output is connected to the wave filter.

The working principle of the present invention is detailed with reference to fig. 2:

when the current is small, due to Rs1< < Rs2, then Us1< < Us2, then Us1 has a negligible influence on circuit parameters, and at the moment, us2= Io Rs2; the processor MCU controls the two ADC to sample Us1 and Us2 respectively, and can judge the value of the ADC2 to be used through a calculation formula and calculate a current value Io;

when the current is large, the current basically passes through the diode because of Us2= Io Rs2> > Ud, the Us2 is positioned at the conducting voltage Ud of the diode by a diode clamp, namely Us2= Ud, and simultaneously Us1= Io Rs1, then the voltage drop Us = Us1+ Us2= Io Rs1+ Ud on the total sampling resistor at the moment, and the influence of the total Us on the circuit parameters is small; the processor MCU controls the two paths of ADCs to sample Us1 and Us2 respectively, and judges that Us2 is in a saturated state according to the value of the ADC2, so that the value of the ADC1 is used for calculating a current value Io;

for example, 10A range is needed, generally Rs1 can be 10 milliohms, at this time, when full range is used 1=10ax0.01r =0.1v, us2=0.3v, then total Us =0.1v +0.3v =0.4v; meanwhile, when the 10mA range needs to be satisfied, under the condition that the signal-to-noise ratio of the two-channel signal processing and the ADC are kept the same, the value Rs2=0.1V/0.01a =10r, that is, us2=0.1V and Us1=0.01ax0.01r =0.1mv when the full range is 10mA, and at this time, us1 is only 1% o of the full range and can be ignored. In this example, two ranges 10A/10ma =1000 times, and in this case, rs2/Rs1 is also 1000 times, and in this case, measurement of a current with an extremely large dynamic range can be simultaneously accommodated.

In addition, to the signal conditioning circuit of each passageway, the utility model discloses do not confine to and adopt conventional mode, increase the range with changing the gain mode in certain extent and grade, further improve measurement accuracy and extension measuring range.

Synthesize the utility model discloses a circuit structure can be known with the theory of operation, the utility model discloses super dynamic range's electric current sampling circuit can be when detecting heavy current or undercurrent, but the circuit automatic switch-over selects sampling resistor's resistance, satisfy the demand of the undercurrent of large resistance sampling and the undercurrent sampling heavy current, the input terminal mode of using mechanical switch or difference has been abandoned, need artifical or automatic judgement and switching have been avoided, and the technical defect of the signal interruption of short-term can appear in the switching process, the detection precision of electric current has also been improved to a certain extent to the while.

Claims

1. The utility model provides a super dynamic range's current sampling circuit, its characterized in that, including first sampling resistor Rs1 and the second sampling resistor Rs2 of establishing ties on the circuit that awaits measuring, second sampling resistor Rs 2's resistance is far away than first sampling resistor Rs1 resistance, the parallelly connected conducting voltage of second sampling resistor Rs2 is the diode D1 of Ud, one section between first sampling resistor Rs1 and second sampling resistor Rs2 is connected to diode D1's negative pole, and the second sampling resistor Rs2 other end is connected to diode D1's positive pole, diode D1 still parallelly connected diode D2, diode D1 negative pole is connected to diode D2's positive pole, and diode D1 is connected to diode D2's negative pole, first sampling resistor Rs1 is connected with the signal conditioner respectively with second sampling resistor Rs2, and two way signal conditioners all connect the MCU unit through the same way.

2. The ultra-dynamic range current sampling circuit of claim 1, wherein said signal conditioners each comprise a signal amplifier and a filter, said signal amplifier input is connected to a first sampling resistor Rs1 or a second sampling resistor Rs2, said signal amplifier output is connected to a filter, and said filter output is connected to an ADC input.