CN111323634B - Wide-range current sampling circuit - Google Patents
Wide-range current sampling circuit Download PDFInfo
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- CN111323634B CN111323634B CN201811537846.3A CN201811537846A CN111323634B CN 111323634 B CN111323634 B CN 111323634B CN 201811537846 A CN201811537846 A CN 201811537846A CN 111323634 B CN111323634 B CN 111323634B
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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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/30—Structural combination of electric measuring instruments with basic electronic circuits, e.g. with amplifier
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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
- G01R19/0023—Measuring currents or voltages from sources with high internal resistance by means of measuring circuits with high input impedance, e.g. OP-amplifiers
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Abstract
The invention provides a wide-range current sampling circuit, which consists of a feedback circuit and a current detection circuit, wherein the load current is divided into two sections for control, one section of the circuit controls a large current section, and the other section of the circuit controls a small current section. When the load current is large, the reference voltage LV-ADJ is used as the reference voltage of the feedback circuit, the adjustable voltage HV-ADJ is adjusted, the voltage of the node I-SENSE is kept equal to the reference voltage LV-ADJ, namely, the VGS voltage of the first MOS tube Q1 is controlled by connecting the first MOS tube Q1 with the current detection resistor R1 in series, so that the voltage of the node I-SENSE is kept unchanged by enabling the voltage to work in an online state and presenting different resistance values. When the load current is small, the voltage of the I-SENSE node is unchanged, and the reference voltage LV-ADJ is adjusted to realize the control of the load current; namely, by adopting the wide-range current sampling circuit, the loss of the current detection resistor R1 is reduced; and the current range output by the load is wider compared with the prior art.
Description
Technical Field
The invention relates to the field of current sampling circuits, in particular to a wide-range current sampling circuit.
Background
Referring to fig. 1, in the prior art, a current detecting resistor is used to sample current and then the current is fed to an operational amplifier for feedback control.
The existing solutions have the following disadvantages: 1. the current sampling resistor is a fixed resistance value, the range of the load current which can be fed back is narrow, and when the detection current is very small, the current sampling resistor is influenced by the input offset voltage of the operational amplifier, so that a feedback loop is unstable, and the output current is also unstable. 2. If the resistance value of the sampling resistor is increased, the problem of sampling of small load current can be solved, but under the condition of large load current, the loss of the sampling resistor is large, and the overall conversion efficiency of a power supply is influenced.
Disclosure of Invention
In order to solve the above problems, the present invention provides a wide-range current sampling circuit, which reduces the current detection resistance loss and widens the current range of the load output.
In order to achieve the above object, the technical solution adopted by the present invention is to provide a wide-range current sampling circuit, which is characterized in that: the current detection circuit comprises a first operational amplifier U1, a second operational amplifier U2, a current detection resistor R1, an equivalent LOAD R-LOAD, an on-resistance R4 and a first MOS tube Q1;
the non-inverting input end of the first operational amplifier U1 is externally connected with an adjustable voltage HV-ADJ, wherein the output end of the first operational amplifier U1 is connected with the G pole of a first MOS transistor Q1 through a conducting resistor R4; one end of the equivalent LOAD R-LOAD is connected with a DC end of a power supply, the other end of the equivalent LOAD R-LOAD is connected with a D pole of a first MOS tube Q1, an S pole of the first MOS tube Q1 is grounded through a current detection resistor R1, an S pole of the first MOS tube Q1 is connected with a non-inverting input end of a second operational amplifier U2, an inverting input end of the second operational amplifier U2 is grounded, and an output end of the second operational amplifier U2 is connected with an inverting input end of the first operational amplifier U1;
the positive phase input end of the voltage negative feedback unit U3 is connected with the D pole of the first MOS transistor Q1, the negative phase input end of the voltage negative feedback unit U3 is connected with the reference voltage LV-ADJ, the output end of the voltage negative feedback unit U3 is connected with the input end of the control circuit, and the output end of the control circuit is connected with the DC end of a power supply.
Further, the current detection circuit further comprises a first filter capacitor C1, one end of the first filter capacitor C1 is connected to the inverting input terminal of the first operational amplifier U1, and the other end of the first filter capacitor C1 is connected to the output terminal of the first operational amplifier U1.
Further, the feedback circuit further comprises a second filter capacitor C2, one end of the second filter capacitor C2 is connected to the inverting input terminal of the voltage negative feedback unit U3, and the other end of the first filter capacitor C1 is connected to the output terminal of the voltage negative feedback unit U3.
Further, the current detection circuit further comprises a second resistor R2, wherein one end of the second resistor R2 is grounded, and the other end is connected with the inverting input terminal of a second operational amplifier U2.
Further, the current detection circuit further comprises a third resistor R3, wherein one end of the third resistor R3 is connected to the inverting input terminal of the second operational amplifier U2, and the other end is connected to the output terminal of the second operational amplifier U2.
The invention has the beneficial effects that: the circuit of the patent is composed of a feedback circuit and a current detection circuit, wherein the load current is divided into two sections for control, one part of the circuit controls a large current section, and the other part of the circuit controls a small current section. When the load current is large, the reference voltage LV-ADJ is used as the reference voltage of the feedback circuit, the adjustable voltage HV-ADJ is adjusted, the voltage of the node I-SENSE is kept equal to the reference voltage LV-ADJ, namely, the VGS voltage of the first MOS tube Q1 is controlled by connecting the first MOS tube Q1 with the current detection resistor R1 in series, so that the voltage of the node I-SENSE is kept unchanged by enabling the voltage to work in an online state and presenting different resistance values. When the load current is small, the voltage of the I-SENSE node is unchanged, and the reference voltage LV-ADJ is adjusted to realize the control of the load current; namely, by adopting the wide-range current sampling circuit, the loss of the current detection resistor R1 is reduced; and the current range output by the load is wider compared with the prior art.
Drawings
Fig. 1 is a schematic diagram of a conventional current sampling circuit.
Fig. 2 is a circuit diagram of the present embodiment.
The reference numbers illustrate: 1. a feedback circuit; 2. a current detection circuit; 3. a control circuit.
Detailed Description
The invention is described in detail below with reference to specific embodiments and the attached drawings.
Referring to fig. 1-2, the present invention relates to a wide-range current sampling circuit, including a feedback circuit 1 and a current detection circuit 2, wherein the feedback circuit 1 includes a control circuit 3 and a voltage negative feedback unit U3, and the current detection circuit 2 includes a first operational amplifier U1, a second operational amplifier U2, a current detection resistor R1, an equivalent LOAD R-LOAD, an on-resistance R4, and a first MOS transistor Q1;
the non-inverting input end of the first operational amplifier U1 is externally connected with an adjustable voltage HV-ADJ, and the output end of the first operational amplifier U1 is connected with the G pole of a first MOS transistor Q1 through a conducting resistor R4; one end of the equivalent LOAD R-LOAD is connected with a DC end of a power supply, the other end of the equivalent LOAD R-LOAD is connected with a D pole of a first MOS tube Q1, an S pole of the first MOS tube Q1 is grounded through a current detection resistor R1, an S pole of the first MOS tube Q1 is connected with a non-inverting input end of a second operational amplifier U2, an inverting input end of the second operational amplifier U2 is grounded, and an output end of the second operational amplifier U2 is connected with an inverting input end of the first operational amplifier U1;
the positive phase input end of the voltage negative feedback unit U3 is connected with the D pole of the first MOS transistor Q1, the negative phase input end of the voltage negative feedback unit U3 is connected with the reference voltage LV-ADJ, the output end of the voltage negative feedback unit U3 is connected with the input end of the control circuit 3, and the output end of the control circuit 3 is connected with the DC end of a power supply.
The voltage generated by the current on the current detection resistor R1 is larger than the input offset voltage of the operational amplifier, the operational amplifier can normally control the large load current, and is smaller than the offset voltage of the operational amplifier, and the operational amplifier cannot normally control the large load current and is considered to be small current; where HV-ADJ is an externally adjustable voltage, which can control large load currents.
When the adjustable voltage HV-ADJ has a voltage applied to the non-inverting input of the first operational amplifier U1, since there is no voltage applied to the inverting input of the first operational amplifier U1, the output of the first operational amplifier U1 will output a high level, which reaches the gate of the first MOS transistor Q1 through R4, and the first MOS transistor Q1 is turned on. When the first MOS transistor Q1 is turned on, the voltage at the DC terminal of the power supply will go through the equivalent LOAD R-LOAD, the first MOS transistor Q1, and the current detecting resistor R1 will return to GND to form a loop.
When current flows through the current detection resistor R1, voltage is generated at two ends of the current, the voltage is amplified by the second operational amplifier U2 and is output to the inverting input end of the first operational amplifier U1, and the voltage is compared with the adjustable voltage HV-ADJ at the positive phase end of the first operational amplifier U1, so that the output voltage of the first operational amplifier U1 is adjusted, according to the working principle of the MOSFET, different gate voltages can enable the drain electrode and the source electrode of the first MOS tube Q1 to have different resistance values, and due to the negative feedback effect of the second operational amplifier U2, the resistance value of the first MOS tube Q1 can be in a stable state.
The I-SENSE is a current feedback sampling point, namely a D pole of a first MOS tube Q1, when the equivalent LOAD R-LOAD has current flowing, the voltage of the I-SENSE is the sum of the voltage of a current detection resistor R1 and the voltage of a first MOS tube Q1 (drain-source), the voltage generated at the node of the I-SENSE is sent to a positive phase input end of a voltage negative feedback unit U3 and compared with a reference voltage LV-ADJ connected to a reverse input end of the voltage negative feedback unit U3, if the voltage generated at the node of the I-SENSE is higher than the voltage value of the reference voltage LV-ADJ, the feedback circuit 1 reduces the voltage of a DC bus through a control circuit 3, and according to the ohm's law, when the LOAD is not changed, the LOAD voltage is reduced, and the LOAD current is also reduced. If the voltage of the I-SENSE node is lower than the voltage value of the reference voltage LV-ADJ, the working process is just opposite, and therefore the purpose of controlling the load current is achieved.
II-when the load needs a large current, the first MOS transistor Q1 can be in a saturated conducting state due to a high VGS voltage, the internal resistance of the first MOS transistor Q1 is very low, the loss of the first MOS transistor Q1 is negligible, and the current flows through the current detection resistor R1, so the node voltage of I-SENSE is approximately equal to the voltage of R1, and the MOSFET does not affect the overall efficiency of the power supply. When the LOAD needs small current, the control voltage of the reference voltage LV-ADJ is also very low, so that the first MOS transistor Q1 has a large resistance value which is connected in series with the current detection resistor R1, so that the voltage of the node of the I-SENSE is increased, the voltage of the DC end of the power supply is controlled to be reduced, and the current flowing through the equivalent LOAD R-LOAD is reduced.
III-the wider current range and more stable circuit output than the prior art control can be demonstrated by the following example calculation.
For example: the input voltage is 0-60V, the load current to be regulated is 1mA-3000mA, the offset voltage of the operational amplifier is 3mV, and the current detection resistance is less than 0.1 omega
The design of the first technical scheme is adopted:
the minimum output current is (needs to be larger than the offset voltage of the operational amplifier):
the minimum load current calculated by 30mA to 1mA is far larger than the required value
Under a load current of 3000mA, the loss of the current detection resistor is as follows:
W＝I2R＝9×0.1＝0.9W
adopt the design of this patent technical scheme:
the current detection resistor R1 adopts 0.05 omega, the amplification factor of the second operational amplifier U2 is 20 times,
and when the calculated output current is 30-3000mA, the HV-ADJ voltage is as follows:
vmax＝IR·βU2＝3×0.05×20＝3V
vmin＝(imin÷imax)×vmax＝(0.03÷3)×3＝0.03V
the I-SENSE node voltage is:
V＝IR＝3×0.05＝0.15V
the maximum loss of the current detection resistor R1 is:
W＝I2R＝3×3×0.05＝0.45W
when the calculated output current is 30mA, the equivalent resistance of the I-SENSE circuit is as follows:
when the calculated output current is 1-30mA, the reference voltage LV-ADJ voltage is as follows:
vmax＝IR＝0.03×5＝0.15V
vmin＝IR＝0.001×5＝5mV
therefore, the loss of R1 of the current detecting resistor in the wide-range current sampling circuit is reduced by 50 percent; and the load output current range is wide, and can support 1mA-3000 mA.
As shown in fig. 2, the current detection circuit 2 further includes a first filter capacitor C1, one end of the first filter capacitor C1 is connected to the inverting input terminal of the first operational amplifier U1, and the other end of the first filter capacitor C1 is connected to the output terminal of the first operational amplifier U1. Further, the feedback circuit 1 further includes a second filter capacitor C2, one end of the second filter capacitor C2 is connected to the inverting input terminal of the voltage negative feedback unit U3, and the other end of the first filter capacitor C1 is connected to the output terminal of the voltage negative feedback unit U3. The first filter capacitor C1 and the second filter capacitor C2 are used for eliminating high frequency interference, so as to ensure the accuracy of the first operational amplifier U1 and the voltage negative feedback unit U3.
Referring to fig. 2, the current detection circuit 2 further includes a second resistor R2, wherein one end of the second resistor R2 is grounded, and the other end is connected to the inverting input terminal of the second operational amplifier U2. Further, the current detection circuit 2 further includes a third resistor R3, one end of the third resistor R3 is connected to the inverting input terminal of the second operational amplifier U2, and the other end is connected to the output terminal of the second operational amplifier U2. Meanwhile, the second resistor R2 and the third resistor R3 can be used for protecting the input and output ends of the operational amplifier U2.
The above embodiments are merely illustrative of the preferred embodiments of the present invention, and not restrictive, and various changes and modifications to the technical solutions of the present invention may be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are intended to fall within the scope of the present invention defined by the appended claims.
Claims (1)
1. A wide range current sampling circuit, characterized by: the current detection circuit comprises a feedback circuit and a current detection circuit, wherein the feedback circuit comprises a control circuit and a voltage negative feedback unit (U3), and the current detection circuit comprises a first operational amplifier (U1), a second operational amplifier (U2), a current detection resistor (R1), an equivalent LOAD (R-LOAD), an on-resistance (R4) and a first MOS (Q1);
the non-inverting input end of the first operational amplifier (U1) is externally connected with an adjustable voltage (HV-ADJ), and the output end of the first operational amplifier (U1) is connected with the G pole of a first MOS transistor (Q1) through an on-resistance (R4); wherein one end of the equivalent LOAD (R-LOAD) is connected with a DC end of a power supply, the other end of the equivalent LOAD (R-LOAD) is connected with a D pole of a first MOS tube (Q1), an S pole of the first MOS tube (Q1) is grounded through a current detection resistor (R1), an S pole of the first MOS tube (Q1) is connected with a non-inverting input end of a second operational amplifier (U2), an inverting input end of the second operational amplifier (U2) is grounded, and an output end of the second operational amplifier (U2) is connected with an inverting input end of the first operational amplifier (U1);
the positive phase input end of the voltage negative feedback unit (U3) is connected with the D pole of the first MOS tube (Q1), the negative phase input end of the voltage negative feedback unit (U3) is connected with a reference voltage (LV-ADJ), the output end of the voltage negative feedback unit (U3) is connected with the input end of a control circuit, and the output end of the control circuit is connected with the DC end;
the adjustable voltage HV-ADJ is controlled to be 30mA-3000mA, and the reference voltage LV-ADJ is controlled to be 1-29 mA;
the current detection circuit further comprises a first filter capacitor (C1), one end of the first filter capacitor (C1) is connected with the inverting input end of a first operational amplifier (U1), and the other end of the first filter capacitor (C1) is connected with the output end of the first operational amplifier (U1);
the feedback circuit further comprises a second filter capacitor (C2), one end of the second filter capacitor (C2) is connected with the inverting input end of the voltage negative feedback unit (U3), and the other end of the first filter capacitor (C1) is connected with the output end of the voltage negative feedback unit (U3);
the current detection circuit further comprises a second resistor (R2), wherein one end of the second resistor (R2) is grounded, and the other end of the second resistor (R2) is connected with the inverting input end of a second operational amplifier (U2);
the current detection circuit further comprises a third resistor (R3), wherein one end of the third resistor (R3) is connected with the inverting input end of the second operational amplifier (U2), and the other end of the third resistor (R3) is connected with the output end of the second operational amplifier (U2).
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| CN201811537846.3A CN111323634B (en) | 2018-12-15 | 2018-12-15 | Wide-range current sampling circuit |
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| CN111323634B true CN111323634B (en) | 2022-04-05 |
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| CN117270449B (en) * | 2023-11-20 | 2024-03-22 | 忱芯电子(苏州)有限公司 | Control circuit of current source and current source thereof |
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| JPH11126875A (en) * | 1997-10-24 | 1999-05-11 | Toshiba Corp | Constant-voltage generator |
| CN2793792Y (en) * | 2004-02-25 | 2006-07-05 | 美国凹凸微系有限公司 | Votage stablilizer with low voltage-drop, integrated circuit and electronic apparatus |
| CN103913629A (en) * | 2014-03-31 | 2014-07-09 | 广东威灵电机制造有限公司 | Device for detecting direct current busbar current and control system of motor with the same |
| CN104882856A (en) * | 2015-05-25 | 2015-09-02 | 重庆大学 | High-precision over-current detection circuit |
| CN205507604U (en) * | 2016-04-11 | 2016-08-24 | 浙江中控技术股份有限公司 | Low -power consumption analog quantity current output system |
| CN106094959A (en) * | 2016-06-21 | 2016-11-09 | 杰华特微电子（杭州）有限公司 | Linear voltage-stabilizing circuit |
| CN208188173U (en) * | 2018-05-24 | 2018-12-04 | 浙江中科正方电子技术有限公司 | A kind of CC E-load |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7545126B2 (en) * | 2006-06-12 | 2009-06-09 | Anpec Electronics Corporation | Controller for sensing a heavy load and a short circuit of low dropout regulators |
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- 2018-12-15 CN CN201811537846.3A patent/CN111323634B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11126875A (en) * | 1997-10-24 | 1999-05-11 | Toshiba Corp | Constant-voltage generator |
| CN2793792Y (en) * | 2004-02-25 | 2006-07-05 | 美国凹凸微系有限公司 | Votage stablilizer with low voltage-drop, integrated circuit and electronic apparatus |
| CN103913629A (en) * | 2014-03-31 | 2014-07-09 | 广东威灵电机制造有限公司 | Device for detecting direct current busbar current and control system of motor with the same |
| CN104882856A (en) * | 2015-05-25 | 2015-09-02 | 重庆大学 | High-precision over-current detection circuit |
| CN205507604U (en) * | 2016-04-11 | 2016-08-24 | 浙江中控技术股份有限公司 | Low -power consumption analog quantity current output system |
| CN106094959A (en) * | 2016-06-21 | 2016-11-09 | 杰华特微电子（杭州）有限公司 | Linear voltage-stabilizing circuit |
| CN208188173U (en) * | 2018-05-24 | 2018-12-04 | 浙江中科正方电子技术有限公司 | A kind of CC E-load |
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