CN118068064A - Current sampling circuit - Google Patents
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- CN118068064A CN118068064A CN202211465653.8A CN202211465653A CN118068064A CN 118068064 A CN118068064 A CN 118068064A CN 202211465653 A CN202211465653 A CN 202211465653A CN 118068064 A CN118068064 A CN 118068064A
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Abstract
The invention discloses a current sampling circuit, which comprises a sampling resistor, wherein a sampling current flows from a first end to a second end of the sampling resistor; the voltage amplification module comprises a first triode and a second triode which are respectively connected with two ends of the sampling resistor, the first triode and the second triode are used as input tube pairs of the voltage amplification module, and the voltage amplification module is used for providing sampling voltage according to the voltage difference between the first end and the second end of the sampling resistor; and the compensation module is used for providing compensation current to equalize the current flowing through the first triode and the second triode, so that high-precision high-side current sampling can be performed at low voltage.
Description
Technical Field
The present invention relates to the field of integrated circuits, and in particular, to a current sampling circuit.
Background
The high-side current sampling is to lower the sampling working voltage as much as possible, and generally adopts the source electrode of the MOS tube as the input of the operational amplifier, so that the operational amplifier can realize wider bandwidth and better dynamic characteristics, but the input offset of the operational amplifier is larger, and the gain of the operational amplifier input by the source electrode is not too large, so that the high-precision sampling is difficult to realize.
Fig. 1 shows a schematic diagram of a current sampling circuit according to the prior art, as shown in fig. 1, the current sampling circuit 100 includes transistors MP1-MP3, resistors R1-R2, current sources S1-S2, and a sampling resistor Rs, and assuming that the amplification factor of the operational amplification circuit Is infinite, a sampling voltage vs= (R2/R1) Rs Is, where Is a sampling current, and the minimum value of a sampling operating voltage VIN of the circuit Is: vin_min=vsg3+vod+i1 r1+rs is_max; the first current I1 Is output by the current source S1 and the current source S2, and Is the tail current of the operational amplifier, vod Is the lowest voltage of the tail current I1, is_max Is the maximum value of the sampling current Is, and Vsg3 Is the source-gate voltage of the transistor MP 3.
Fig. 2 shows a schematic diagram of another current sampling circuit according to the prior art, as shown in fig. 2, the current sampling circuit 200 includes transistors MP3-MP4, transistors Q1-Q2, resistors R1-R2, current sources S1-S2, and a sampling resistor Rs, and the current sampling circuit 200 Is basically the same as the circuit structure of the current sampling circuit 100, except that the MOS transistor pair MP1 and MP2 in the operational amplifier Is replaced by the BJT transistor pair Q1 and Q2, the MOS transistor pair Is replaced by the BJT transistor pair, although the input offset can be reduced, since the BJT transistor Is a current driving element, the transistor MP4 needs to be additionally added to provide a bias voltage, so that the sampling operation voltage becomes high, and low-voltage sampling cannot be realized, the minimum value of the sampling operation voltage VIN Is set to be set to g4+vod+i1+r1+ismaxvbe2, where Vod Is the minimum voltage of the tail current I1, vsg_max4 Is the maximum value of the sampling current isg, and vsg4 Is set to be the voltage of the drain electrode of the transistor vsq 2.
In summary, the current sampling circuit 100 cannot perform high-precision sampling, but the current sampling circuit 200 can perform high-precision sampling, but its lowest sampling operation voltage is larger than the lowest sampling operation voltage of the current sampling circuit 100 by Vbe2, and low-voltage sampling cannot be performed, so a new current sampling circuit has to be proposed to solve the above-mentioned problems.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a current sampling circuit that can perform high-side current sampling with high accuracy at low voltage.
According to an aspect of the present invention, there is provided a current sampling circuit comprising a sampling resistor, a sampling current flowing from a first end to a second end of the sampling resistor; the voltage amplification module comprises a first triode and a second triode which are respectively connected with two ends of the sampling resistor, the first triode and the second triode are used as input tube pairs of the voltage amplification module, and the voltage amplification module is used for providing sampling voltage according to the voltage difference between the first end and the second end of the sampling resistor; and the compensation module is used for providing compensation current so as to equalize the currents flowing through the first triode and the second triode.
Optionally, the voltage amplifying module includes a voltage comparing module for comparing voltages of the first end and the second end of the sampling resistor; and the sampling output module is used for providing sampling voltage according to the comparison result of the voltage comparison module.
Optionally, the voltage comparison module includes a first resistor, the first triode and a first current source, which are sequentially connected between a first end and a ground end of the sampling resistor, and a control end and a second end of the first triode are connected; the second resistor, the second triode and the second current source are sequentially connected between the second end of the sampling resistor and the grounding end, the control end of the second triode is connected with the control end of the first triode, the resistance values of the first resistor and the second resistor are equal, and the first current source and the second current source output first current respectively.
Optionally, the sampling output module includes a first transistor and a third resistor connected in sequence between a first end of the first triode and a ground end, a control end of the first transistor is connected with a second end of the second triode, wherein a common node of the first transistor and the third resistor is used for providing the sampling voltage.
Optionally, the compensation module includes a third triode and a third current source sequentially connected between the power supply and the ground terminal; the second transistor and the third transistor are sequentially connected between the control end and the grounding end of the third triode, the control end of the second transistor is connected with the second end of the third triode, and the first end of the third transistor is connected with the control end; and a fourth transistor connected between the second terminal of the first transistor and the ground terminal, the control terminal of the fourth transistor being connected to the control terminal of the third transistor, wherein the first terminal of the fourth transistor is configured to provide the compensation current, and the third current source is configured to provide a third current to the third transistor.
Optionally, the first triode and the second triode are the same and have the same amplification factor.
Optionally, the compensation current i2=2 (I1/β), where I1 is the first current and β is the amplification factor of the first transistor.
Optionally, the compensation current is obtained by reasonably configuring the ratio of the amplification factors of the third transistor to the first transistor, the ratio of the current values of the third current to the first current, and the size ratio of the fourth transistor to the third transistor.
Optionally, the compensation module is configured to configure the size ratio of the fourth transistor and the third transistor to 2 when the current values of the third current and the first current are equal, and the amplification factors of the third transistor and the first transistor are equal: 1.
Optionally, the compensation module is configured to configure the size ratio of the fourth transistor and the third transistor to 1 when the amplification factor of the third transistor is one half of the first transistor, and the third current is equal to the current value of the first current: 1.
The current sampling circuit comprises a sampling resistor, wherein sampling current flows from a first end to a second end of the sampling resistor; the voltage amplifying module comprises a first triode and a second triode which are respectively connected with two ends of the sampling resistor, the first triode and the second triode are used as input tube pairs of the voltage amplifying module, and the voltage amplifying module is used for providing sampling voltage according to the voltage difference between the first end and the second end of the sampling resistor; and the compensation module is used for providing compensation current to equalize the currents flowing through the first triode and the second triode, so that high-precision current sampling can be performed at low voltage.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings, in which:
fig. 1 shows a schematic diagram of a current sampling circuit according to the prior art;
Fig. 2 shows a schematic diagram of a structure of another current sampling circuit according to the prior art;
Fig. 3 shows a schematic diagram of a current sampling circuit according to an embodiment of the invention.
Detailed Description
Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. The same elements or modules are denoted by the same or similar reference numerals in the various figures. For clarity, the various features of the drawings are not drawn to scale.
It should be appreciated that in the following description, a "circuit" may include a single or multiple combined hardware circuits, programmable circuits, state machine circuits, and/or elements capable of storing instructions for execution by the programmable circuits. When an element or circuit is referred to as being "connected to" another element or circuit is "connected between" two nodes, it can be directly coupled or connected to the other element or intervening elements may be present, the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled to" or "directly connected to" another element, it means that there are no intervening elements present between the two.
Also, certain terms are used throughout the description and claims to refer to particular components. It will be appreciated by those of ordinary skill in the art that a hardware manufacturer may refer to the same component by different names. The present patent specification and claims do not take the form of an element or components as a functional element or components as a rule.
Furthermore, it should be noted that relational terms such as first and second are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
In the application, a MOS (Metal-Oxide-Semiconductor Field-Effect Transistor) transistor comprises a first end, a second end and a control end, and in the conducting state of the MOS transistor, current flows from the first end to the second end. The first end, the second end and the control end of the PMOS tube are respectively a source electrode, a drain electrode and a grid electrode, and the first end, the second end and the control end of the NMOS tube are respectively a drain electrode, a source electrode and a grid electrode. A transistor (also known as a bipolar junction transistor) includes a first terminal, a second terminal, and a control terminal, and in the on state of the transistor, current flows from the first terminal to the second terminal. The first end, the second end and the control end of the PNP tube are respectively an emitter, a collector and a base, and the first end, the second end and the control end of the NPN tube are respectively a collector, an emitter and a base.
Fig. 3 shows a schematic diagram of a current sampling circuit according to an embodiment of the present invention, and as shown in fig. 3, the current sampling circuit 300 includes a sampling resistor Rs, a voltage amplifying module 310, and a compensating module 320.
The sampling resistor Rs Is used for converting a current signal in the sampling current Is into a voltage signal, the voltage amplifying module 310 Is used for providing the sampling voltage Vs to the output node according to the voltage difference between two ends of the sampling resistor Rs, and the compensating module 320 Is used for providing the compensating current I2 to the voltage amplifying module 310 so that the current sampling circuit 300 can perform high-precision sampling.
The first end a of the sampling resistor Rs Is a sampling working voltage end VIN, the second end B Is an output end of the sampling current Is, and a voltage difference Is formed between the first end a and the second end B of the sampling resistor Rs after the sampling current Is flows from the first end a to the second end B of the sampling resistor Rs.
The voltage amplifying module 310 includes a voltage comparing module for comparing voltages of the first terminal a and the second terminal B of the sampling resistor Rs, and a sampling output module for providing the sampling voltage Vs to the output node according to a comparison result of the voltage comparing module.
The voltage comparison module comprises a resistor R1, a triode Q1 and a current source S1 which are sequentially connected between a first end A of a sampling resistor Rs and a grounding end, and a resistor R2, a triode Q2 and a current source S2 which are sequentially connected between a second end B of the sampling resistor Rs and the grounding end, wherein the resistance value of the resistor R1 and the resistance value of the resistor R2 are equal, the control end of the triode Q1 is connected with the second end, the control end of the triode Q1 is connected with the control end of the triode Q2, the triode Q1 and the triode Q2 are input tube pairs of the voltage amplification module 310, and the current source S1 and the current source S2 are used for respectively outputting a first current I1 to serve as tail current of the voltage amplification module 310.
The sampling output module comprises a transistor MP1 and a resistor R3 which are sequentially connected between a first end of a triode Q1 and a grounding end, wherein a control end of the transistor MP1 is connected with a second end of a triode Q2, a common node of the resistor R3 and the transistor MP1 is an output node and is used for providing a sampling voltage Vs, and a formula of the sampling voltage is that
Further, transistor Q1 and transistor Q2 are identical, having the same amplification factor.
The voltage amplifying module 310 ensures the sampling operation voltage VIN of the current sampling circuit 300 by connecting the control terminal of the transistor Q1 with the second terminal, so that the minimum value of the sampling operation voltage vin_min=vsg1+vod+i1×r1+rs_max Is ensured, where Vod Is the minimum voltage of the tail current I1, is_max Is the maximum value of the sampling current Is, vsg1 Is the source-gate voltage of the transistor MP1, but due to the current at the control terminal of the transistor, offset Is generated between the input terminal of the input transistor pair, i.e. the first terminal of the transistor Q1 and the first terminal of the transistor Q2.
The control end (base) current of the triode Q2 is I1/beta through calculation, and the second end (collector) current Ic of the triode Q1 is:
the first terminal (emitter) currents of transistors Q1 and Q2 are:
Ie1＝(1-1/β)*I1；
Ie2＝(1+1/β)*I1，
Wherein, beta is the amplification factor of the triode.
Since the emitter currents of the transistor Q1 and the transistor Q2 are different, the base-emitter voltages Vbe of the transistor Q1 and the transistor Q2 are different, and the voltage drops generated by the resistor R1 and the resistor R2 are also different, which seriously affects the sampling accuracy of the voltage amplifying module 310.
In order to ensure the sampling precision of the voltage amplifying module 310, the base-emitter voltages Vbe of the transistor Q1 and the transistor Q2 need to be the same, that is, the emitter currents of the transistor Q1 and the transistor Q2 need to be the same, therefore, the present invention provides the compensation module 320, and the compensation module 320 equalizes the currents flowing through the transistor Q1 and the transistor Q2, specifically, the emitter currents are (1-1/β) ×i1, the collector currents are I1, and the base currents are I1/β, so that the base-emitter voltages Vbe of the transistor Q1 and the transistor Q2 are equal, wherein the compensation current i2=2×i1/β.
The compensation module 320 includes a transistor Q3 and a current source S3 sequentially connected between the power supply VDD and the ground, a transistor MP2 and a transistor MN1 sequentially connected between a control terminal of the transistor Q3 and the ground, and a transistor MN2 connected between a control terminal of the transistor Q1 and the ground, wherein the control terminal of the transistor MP2 is connected to the second terminal of the transistor Q3, the control terminals of the transistor MN1 and the transistor MN2 are connected, and the first terminal of the transistor MN1 is connected to the control terminal, and the first terminal of the transistor MN2 is used for providing the compensation current I2.
The compensation module I2 is obtained by reasonably configuring the ratio of the amplification factors of the transistor Q3 and the transistor Q1, the ratio of the current values of the third current I3 and the first current I1, and the size ratio of the transistor MN2 to the transistor MN 1.
In one embodiment, transistor Q3 is identical to transistor Q1, having the same amplification β, and the size ratio of transistor MN2 to transistor MN1 is 2:1, when the compensation module 320 is operated, the current source S3 provides a third current I3 having a current value equal to the first current I1 to the second terminal of the transistor Q3, so that the current of the control terminal of the transistor Q3 is equal to I1/β, the first terminal of the transistor MP2 receives the current of the control terminal of the transistor Q3 and transmits it to the transistor MN1, the transistor MN2 mirrors the current of the transistor MN1 to generate the compensation current I2, and the compensation current I2 is transmitted to the second terminal of the transistor Q1.
In another embodiment, the transistor Q3 is the same as the transistor Q1, the amplification factor of the transistor Q3 is half of that of the transistor Q1, the current value of the third current I3 is equal to that of the first current I1, and the compensation current I2 with the current value equal to 2 x (I1/β) can be obtained only by configuring the size ratio of the transistor MN1 to the transistor MN2 to 1.
In another embodiment, the transistor Q3 and the transistor Q1 are of the same type and have the same amplification factor β, the size ratio of the transistor MN1 to the transistor MN2 is 1:1, and the compensation current I2 with a current value equal to 2×2 (I1/β) can be obtained only by setting the current value of the third current I3 to be twice the first current I1.
Further, the transistor Q1, the transistor Q2 and the transistor Q3 are PNP transistors. In other embodiments, transistors Q1, Q2 and Q3 may be NPN transistors.
Further, the transistors MP1 and MP2 are PMOS transistors, and the transistors MN1 and MN2 are NMOS transistors.
According to the current sampling circuit 300 provided by the invention, the control end and the second end of the triode Q1 are connected, so that the lowest sampling working voltage VIN_min of the current sampling circuit 300 is ensured, and meanwhile, the compensation current I2 is provided for the second end of the triode Q1, so that the collector currents of the triode Q1 and the triode Q2 are equal, and the sampling precision in current sampling is improved.
Embodiments in accordance with the present invention, as described above, are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various modifications as are suited to the particular use contemplated. The scope of the invention should be determined by the appended claims and their equivalents.
Claims (10)
1. A current sampling circuit, comprising:
the sampling resistor is used for sampling current to flow from a first end to a second end of the sampling resistor;
The voltage amplification module comprises a first triode and a second triode which are respectively connected with two ends of the sampling resistor, the first triode and the second triode are used as input tube pairs of the voltage amplification module, and the voltage amplification module is used for providing sampling voltage according to the voltage difference between the first end and the second end of the sampling resistor;
And the compensation module is used for providing compensation current so as to equalize the currents flowing through the first triode and the second triode.
2. The current sampling circuit of claim 1, wherein the voltage amplification module comprises:
The voltage comparison module is used for comparing the voltages of the first end and the second end of the sampling resistor;
and the sampling output module is used for providing sampling voltage according to the comparison result of the voltage comparison module.
3. The current sampling circuit of claim 2, wherein the voltage comparison module comprises:
The first resistor, the first triode and the first current source are sequentially connected between the first end of the sampling resistor and the grounding end, and the control end and the second end of the first triode are connected;
The second resistor, the second triode and the second current source are sequentially connected between the second end of the sampling resistor and the grounding end, the control end of the second triode is connected with the control end of the first triode,
The first resistor and the second resistor have the same resistance, and the first current source and the second current source respectively output first current.
4. A current sampling circuit according to claim 3, wherein the sampling output module comprises:
A first transistor and a third resistor which are connected between the first end of the first triode and the grounding end in sequence, the control end of the first transistor is connected with the second end of the second triode,
Wherein a common node of the first transistor and the third resistor is used to provide the sampling voltage.
5. The current sampling circuit of claim 4, wherein the compensation module comprises:
the third triode and the third current source are sequentially connected between the power supply and the grounding end;
The second transistor and the third transistor are sequentially connected between the control end and the grounding end of the third triode, the control end of the second transistor is connected with the second end of the third triode, and the first end of the third transistor is connected with the control end; and
A fourth transistor connected between the second end of the first triode and the ground, the control end of the fourth transistor being connected with the control end of the third transistor,
The first end of the fourth transistor is used for providing the compensation current, and the third current source is used for providing a third current to the third triode.
6. The current sampling circuit of claim 5 wherein the first transistor and the second transistor are identical, having the same amplification factor.
7. The current sampling circuit of claim 6, wherein the compensation current i2=2 (I1/β), wherein I1 is the first current and β is the amplification factor of the first transistor.
8. The current sampling circuit of claim 7 wherein the compensation current is obtained by rationally configuring a ratio of the amplification of the third transistor to the first transistor, a ratio of the current value of the third current to the first current, and a size ratio of the fourth transistor to the third transistor.
9. The current sampling circuit of claim 8, wherein the compensation module is configured to configure the size ratio of the fourth transistor and the third transistor to 2 when the current value of the third current and the first current is equal, and the amplification factor of the third transistor and the first transistor is equal: 1.
10. The current sampling circuit of claim 8, wherein the compensation module is configured to configure the size ratio of the fourth transistor and the third transistor to 1 when the amplification factor of the third transistor is one-half of the first transistor, the third current is equal to the current value of the first current: 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211465653.8A CN118068064A (en) | 2022-11-22 | 2022-11-22 | Current sampling circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211465653.8A CN118068064A (en) | 2022-11-22 | 2022-11-22 | Current sampling circuit |
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| Publication Number | Publication Date |
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| CN118068064A true CN118068064A (en) | 2024-05-24 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202211465653.8A Pending CN118068064A (en) | 2022-11-22 | 2022-11-22 | Current sampling circuit |
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| CN (1) | CN118068064A (en) |
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- 2022-11-22 CN CN202211465653.8A patent/CN118068064A/en active Pending
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