Non-isolated high-side sampling constant current circuit

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By using a non-isolated high-side sampling constant current circuit in battery charging and battery voltage sampling, and using ordinary op amps to achieve high-side constant current, the problem of sampling resistance affecting voltage accuracy in traditional low-side sampling methods is solved, and the cost is reduced. Improves interchangeability.

CN119440156APending Publication Date: 2025-02-14ECU ELECTRONICS INDAL

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Patent Information

Application Number: CN202411551656.2
Authority / Receiving Office: CN · China
Patent Type: Applications(China)
Current Assignee / Owner
Filing Date: 2024-11-01
Publication Date: 2025-02-14

AI Technical Summary

Technical Problem

When the traditional low-side sampling method realizes battery charging and battery voltage sampling, there is a problem that the sampling resistance affects the voltage accuracy, and it requires the use of an expensive special integrated op amp, which is costly and poorly replaceable.

Method used

Non-isolated high-side sampling constant current circuit is adopted to achieve high-side constant current through ordinary op amps. The number and selection of devices are no different from low-side sampling constant current, avoiding the use of expensive, special integrated op amps.

Benefits of technology

The function of high-side constant current is realized, which reduces circuit costs and improves substitutability and practicality. The output current is determined only by resistor R5, resistor R9 and sampling resistor Rs. Adjusting these resistances can achieve constant current.

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Abstract

The invention discloses a non-isolated high-side sampling constant current circuit, which belongs to the technical field of power supply control, and comprises a step-down chip IC1, a port 5 of the step-down chip IC1 is connected with an input power supply Vin, a port 3 of the step-down chip IC1, an inductor L1 and a capacitor C4 are connected in series, and an anode of the capacitor C4, a resistor Rs and a power supply Vo + are connected in series; the resistor R5, the resistor R6 and the input P + end of the operational amplifier IC2 are sequentially connected in series; the power supply Vo +, the resistor R2 and the input N-end of the operational amplifier IC2 are connected in series; and the output end O of the operational amplifier IC2, a resistor R3, a diode D3 and a port 2 of the step-down chip IC1 are connected in sequence. A common operational amplifier is adopted to achieve high-side constant current and achieve the function of a low-side current sampling circuit, the number and model selection of devices are the same as those of low-side sampling constant current, the use of an expensive special integrated operational amplifier is avoided, and the practicability and replaceability of the circuit are greatly improved.

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Description

Technical Field

[0001] The invention relates to the technical field of power supply control, in particular to a non-isolated high-side sampling constant current circuit. Background Art

[0002] Constant current circuits are widely used in many occasions. Constant current is generally achieved by sampling the current of the circuit loop, and most circuits will sample the low-side current to send it to the control system to achieve it. It can be achieved by sampling the current with some suitable ordinary op amps. However, for some occasions where the input and output need to share a negative, such as charging the battery and sampling the battery voltage, if the traditional low-side sampling method is used to achieve constant current, the current sampling resistor needs to be placed at the negative end of the battery, and the reference ground of the microcontroller is the negative of the input. When sampling the battery voltage, it will be found that there is a current sampling resistor in the middle. Obviously, the sampled battery voltage is inaccurate at this time, so high-side sampling is required to achieve constant current charging. However, if the sampling resistor is placed on the high side, there will be various problems. For example, a special powerful integrated op amp is required to achieve current sampling, which has poor replaceability and is expensive, and is often unacceptable in terms of the cost share of the entire controller. Summary of the invention

[0003] In view of the above-mentioned problems existing in the prior art, the present invention provides a method for realizing a non-isolated high-side sampling constant current circuit, which can use an ordinary operational amplifier to realize the high-side constant current. The number of components and the selection of components are no different from those of ordinary low-side sampling constant current, avoiding the use of expensive dedicated integrated operational amplifiers and greatly improving the practicality and replaceability of the circuit.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A non-isolated high-side sampling constant current circuit comprises a buck chip IC1, wherein a port 5 of the buck chip IC1 is connected to an input power supply Vin, and a port 1 of the buck chip IC1 is grounded;

[0006] Port 2 of the step-down chip IC1 is connected to one end of the resistor R4, and the other end of the resistor R4 is grounded;

[0007] Port 3 of the buck chip IC1 is connected to the positive electrode of the diode D1, and the negative electrode of the diode D1 is connected to port 5 of the buck chip IC1; the diode D1 is a bypass diode used to protect the components inside the control system;

[0008] The positive electrode of the capacitor C3 is connected to the input power supply Vin, and the negative electrode of the capacitor C3 is grounded; one end of the capacitor C5 is connected to the input power supply Vin, and the other end of the capacitor C5 is grounded;

[0009] Port 3 of the step-down chip IC1 is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the positive electrode of the capacitor C4, and the negative electrode of the capacitor C4 is grounded;

[0010] Port 3 of the step-down chip IC1 is connected to the cathode of the diode D2, and the anode of the diode D2 is grounded;

[0011] The positive electrode of capacitor C4 is connected to one end of resistor Rs, the other end of resistor Rs is connected to power supply Vo+, and resistor Rs is a current sampling resistor;

[0012] One end of the resistor R5 is connected to the positive electrode of the capacitor C4, the other end of the resistor R5 is connected to one end of the resistor R6, and the other end of the resistor R6 is connected to the input P+ terminal of the operational amplifier IC2;

[0013] One end of the resistor R2 is connected to the power supply Vo+, and the other end of the resistor R2 is connected to the input N- terminal of the operational amplifier IC2;

[0014] One end of the resistor R1 is connected to the input N-terminal of the operational amplifier IC2, the other end of the resistor R1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the output O-terminal of the operational amplifier IC2;

[0015] The output O terminal of the operational amplifier IC2 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the port 2 of the step-down chip IC1.

[0016] As a further solution of the present invention: the power supply Vo+ is connected to one end of the capacitor C1, and the other end of the capacitor C1 is grounded.

[0017] As a further solution of the present invention: the input power supply Vin is connected to one end of the resistor R8, and the other end of the resistor R8 is simultaneously connected to the positive electrode of the capacitor C4 and the output end of the reference source IC3;

[0018] The input end of the reference source IC3 is connected to one end of the resistor R10, and the other end of the resistor R10 is grounded;

[0019] Capacitor C7 is connected in parallel across the reference source IC3;

[0020] An input end of the reference source IC3 is connected to one end of the resistor R9, and the other end of the resistor R9 is connected between the resistor R5 and the resistor R6.

[0021] As a further solution of the present invention: the input Vin is connected to the resistor R8, the reference source IC3, and the resistor R10 to construct a floating 2.5V reference source.

[0022] As a further solution of the present invention: the power supply end of the operational amplifier IC2 is simultaneously connected to one end of the resistor R7 and one end of the capacitor C6, the other end of the resistor R7 is connected to the input power supply Vin, and the other end of the capacitor C6 is grounded; the ground end of the operational amplifier IC2 is grounded.

[0023] As a further solution of the present invention: the model of the operational amplifier IC2 is LM321; the model of the reference source IC3 is TL431.

[0024] As a further solution of the present invention: the capacitors C3 and C5 are input decoupling capacitors, the inductor L1 is an energy storage inductor, the diode D2 is a freewheeling diode, and the capacitor C4 is an energy storage capacitor.

[0025] As a further solution of the present invention: the input power supply Vin, the resistor R7 and the capacitor C6 form an RC filter discharge circuit.

[0026] As a further solution of the present invention: the resistor R1 and the capacitor C2 form a feedback PI compensation network.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a method for realizing a non-isolated high-side sampling constant current circuit. The output current is determined only by a resistor R5, a resistor R9 and a sampling resistor Rs, and has nothing to do with other resistors. The constant current can be realized by adjusting the three resistors, and the same function as the low-side current sampling circuit is realized. An ordinary operational amplifier can be used to realize the high-side constant current. The number of components and the selection of components are the same as those of an ordinary low-side sampling constant current. The use of expensive dedicated integrated operational amplifiers is avoided and the practicality and replaceability of the circuit are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a schematic diagram of a non-isolated high-side sampling constant current circuit disclosed in an embodiment. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", and "connected" should be understood in a broad sense; for example, it can be a fixed connection, a detachable connection, or an integral connection, a mechanical connection, or an electrical connection, a direct connection, or an indirect connection through an intermediate medium, or the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] See also Figure 1 , a non-isolated high-side sampling constant current circuit, comprising a buck chip IC1, wherein port 5 of the buck chip IC1 is connected to an input power supply Vin, and port 1 of the buck chip IC1 is grounded;

[0033] Port 2 of the step-down chip IC1 is connected to one end of the resistor R4, and the other end of the resistor R4 is grounded;

[0034] Port 3 of the buck chip IC1 is connected to the positive electrode of the diode D1, and the negative electrode of the diode D1 is connected to port 5 of the buck chip IC1; the diode D1 is a bypass diode used to protect the components inside the control system;

[0035] The positive electrode of the capacitor C3 is connected to the input power supply Vin, and the negative electrode of the capacitor C3 is grounded; one end of the capacitor C5 is connected to the input power supply Vin, and the other end of the capacitor C5 is grounded;

[0036] Port 3 of the step-down chip IC1 is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the positive electrode of the capacitor C4, and the negative electrode of the capacitor C4 is grounded;

[0037] Port 3 of the step-down chip IC1 is connected to the cathode of the diode D2, and the anode of the diode D2 is grounded;

[0038] The positive electrode of the capacitor C4 is connected to one end of the resistor Rs, and the other end of the resistor Rs is connected to the power supply Vo+. The resistor Rs is a current sampling resistor, and the two ends of the resistor Rs are sampling points X and Y respectively;

[0039] One end of the resistor R5 is connected to the positive electrode of the capacitor C4, the other end of the resistor R5 is connected to one end of the resistor R6, and the other end of the resistor R6 is connected to the input P+ terminal of the operational amplifier IC2;

[0040] One end of the resistor R2 is connected to the power supply Vo+, and the other end of the resistor R2 is connected to the input N- terminal of the operational amplifier IC2; the power supply Vo+ is connected to one end of the capacitor C1, and the other end of the capacitor C1 is grounded

[0041] One end of the resistor R1 is connected to the input N-terminal of the operational amplifier IC2, the other end of the resistor R1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the output O-terminal of the operational amplifier IC2;

[0042] The output O terminal of the operational amplifier IC2 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the port 2 of the step-down chip IC1;

[0043] The power supply terminal of the operational amplifier IC2 is connected to one end of the resistor R7 and one end of the capacitor C6 at the same time, the other end of the resistor R7 is connected to the input power supply Vin, and the other end of the capacitor C6 is grounded; the ground terminal of the operational amplifier IC2 is grounded;

[0044] The input power supply Vin is connected to one end of the resistor R8, and the other end of the resistor R8 is simultaneously connected to the positive electrode of the capacitor C4 and the output end of the reference source IC3;

[0045] The input end of the reference source IC3 is connected to one end of the resistor R10, and the other end of the resistor R10 is grounded;

[0046] Capacitor C7 is connected in parallel across the reference source IC3;

[0047] The input end of the reference source IC3 is connected to one end of the resistor R9, and the other end of the resistor R9 is connected between the resistor R5 and the resistor R6;

[0048] The model of operational amplifier IC2 is LM321; the model of reference source IC3 is TL431;

[0049] Figure 1 Taking the buck type (i.e. BUICK type) constant current as an example, IC1 is a control system composed of buck chips, which can be integrated or discrete ( Figure 1According to the buck integration), capacitors C3 and C5 are input decoupling capacitors, inductor L1, diode D2 and capacitor C4 form the energy storage inductor, freewheeling diode and energy storage capacitor of the BUCK circuit, diode D1 is a bypass diode, which is used to protect the internal components of the control system from damage, and the dotted box is a high-side sampling constant current control circuit, which is composed of input Vin connected to resistor R8, reference source TL431, and resistor R10 to construct a floating 2.5V reference source, capacitor C7 is filtered and stabilized on TL431, resistor Rs is a current sampling resistor, IC2 is an operational amplifier (LM321 is used as an example in the figure), Vin is connected to resistor R7 and capacitor C6 to form an RC filter to power the op amp, resistor R1 and capacitor C2 are feedback PI compensation network, and the op amp output is connected to resistor R3 and diode D3 to be sent to the FB feedback pin of the control system composed of the buck chip for modulation to achieve output constant current. The core of this invention is the floating 2.5V reference constructed by TL431. To make the output constant current, the potential XY must be satisfied = constant value (A), and the output current is equal to According to the characteristics of the operational amplifier, the potential of the inverting input terminal is N=Y by virtual disconnection, and the positive input terminal is P=N=Y by virtual short. Similarly, the potential of the left end of the resistor R6 is also Y by virtual disconnection. According to Kirchhoff's current law (KCL) and the characteristics of the operational amplifier virtual disconnection, the current flowing into the resistor R6 is zero, so the current flowing into the resistor R5 is equal to the current flowing into the resistor R9, that is, the equation As defined above, XY=A, so the above equation can be written as Right now It can be concluded that the output current is only determined by resistor R5, resistor R9 and sampling resistor Rs, and has nothing to do with other resistors. By adjusting these three resistors, constant current can be achieved, realizing the same function as the low-side current sampling circuit.

[0050] The present invention provides a method for realizing a non-isolated high-side sampling constant current circuit, which can use an ordinary operational amplifier to realize the high-side constant current. The number of components and the selection of components are the same as those of ordinary low-side sampling constant current, avoiding the use of expensive dedicated integrated operational amplifiers and greatly improving the practicality and replaceability of the circuit.

[0051] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive from any point of view. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention, and any reference numerals in the claims should not be considered as limiting the claims involved.

[0052] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A non-isolated high-side sampling constant current circuit, characterized in that: It includes a buck chip IC1, wherein the port 5 of the buck chip IC1 is connected to the input power supply Vin, and the port 1 of the buck chip IC1 is grounded; Port 2 of the step-down chip IC1 is connected to one end of the resistor R4, and the other end of the resistor R4 is grounded; Port 3 of the buck chip IC1 is connected to the positive electrode of the diode D1, and the negative electrode of the diode D1 is connected to port 5 of the buck chip IC1; the diode D1 is a bypass diode used to protect the components inside the control system; The positive electrode of the capacitor C3 is connected to the input power supply Vin, and the negative electrode of the capacitor C3 is grounded; one end of the capacitor C5 is connected to the input power supply Vin, and the other end of the capacitor C5 is grounded; Port 3 of the step-down chip IC1 is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the positive electrode of the capacitor C4, and the negative electrode of the capacitor C4 is grounded; Port 3 of the step-down chip IC1 is connected to the cathode of the diode D2, and the anode of the diode D2 is grounded; The positive electrode of capacitor C4 is connected to one end of resistor Rs, the other end of resistor Rs is connected to power supply Vo+, and resistor Rs is a current sampling resistor; One end of the resistor R5 is connected to the positive electrode of the capacitor C4, the other end of the resistor R5 is connected to one end of the resistor R6, and the other end of the resistor R6 is connected to the input P+ terminal of the operational amplifier IC2; One end of the resistor R2 is connected to the power supply Vo+, and the other end of the resistor R2 is connected to the input N- terminal of the operational amplifier IC2; One end of the resistor R1 is connected to the input N-terminal of the operational amplifier IC2, the other end of the resistor R1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the output O-terminal of the operational amplifier IC2; The output O terminal of the operational amplifier IC2 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the port 2 of the step-down chip IC1.

2. A non-isolated high-side sampling constant current circuit according to claim 1, characterized in that: The power source Vo+ is connected to one end of the capacitor C1, and the other end of the capacitor C1 is grounded.

3. A non-isolated high-side sampling constant current circuit according to claim 2, characterized in that: The input power supply Vin is connected to one end of the resistor R8, and the other end of the resistor R8 is simultaneously connected to the positive electrode of the capacitor C4 and the output end of the reference source IC3; The input end of the reference source IC3 is connected to one end of the resistor R10, and the other end of the resistor R10 is grounded; Capacitor C7 is connected in parallel across the reference source IC3; An input end of the reference source IC3 is connected to one end of the resistor R9, and the other end of the resistor R9 is connected between the resistor R5 and the resistor R6.

4. A non-isolated high-side sampling constant current circuit according to claim 3, characterized in that: The input Vin is connected to the resistor R8, the reference source IC3, and the resistor R10 to form a floating 2.5V reference source.

5. The non-isolated high-side sampling constant current circuit according to claim 3, characterized in that: The power supply terminal of the operational amplifier IC2 is connected to one end of the resistor R7 and one end of the capacitor C6 at the same time, the other end of the resistor R7 is connected to the input power supply Vin, and the other end of the capacitor C6 is grounded; the ground terminal of the operational amplifier IC2 is grounded.

6. A non-isolated high-side sampling constant current circuit according to claim 5, characterized in that: The model of the operational amplifier IC2 is LM321; the model of the reference source IC3 is TL431.

7. A non-isolated high-side sampling constant current circuit according to claim 6, characterized in that: The capacitors C3 and C5 are input decoupling capacitors, the inductor L1 is an energy storage inductor, the diode D2 is a freewheeling diode, and the capacitor C4 is an energy storage capacitor.

8. A non-isolated high-side sampling constant current circuit according to claim 7, characterized in that: The input power supply Vin, the resistor R7 and the capacitor C6 form an RC filter discharge circuit.

9. A non-isolated high-side sampling constant current circuit according to claim 8, characterized in that: The resistor R1 and the capacitor C2 form a feedback PI compensation network.