Current sampling circuit, chip and electronic equipment

Abstract

The invention relates to the technical field of power supply circuits, in particular to a current sampling circuit, a chip and electronic equipment. The current sampling circuit comprises a first sampling branch, a second sampling branch and an operational amplifier, the sampling resistor is connected in series with a current branch to be measured; the output end of the first sampling branch is connected with the first input end of the operational amplifier; the first sampling branch is used for sampling first sampling voltage of the first end of the sampling resistor, and the second sampling branch is used for sampling second sampling voltage of the second end of the sampling resistor and outputting the second sampling voltage to the second input end of the operational amplifier; the operational amplifier is used for amplifying the difference value between the first sampling voltage and the second sampling voltage according to the amplification factor; the first sampling output end of the current sampling circuit outputs a first voltage value. When the current sampling circuit provided by the invention is used for high-side current sampling, errors caused by common-mode voltage are eliminated, so that the sampling precision is relatively high.

Description

Technical Field

[0001] The present application relates to the technical field of power supply circuits, and in particular to a current sampling circuit, a chip, and an electronic device. Background Art

[0002] The current sampling circuit is used to monitor the current value on the current loop in real time, and respond promptly when the current value on the monitored current loop exceeds the working range to ensure the safe operation of the circuit system.

[0003] In the field of power chips, it is usually necessary to perform high-precision current sampling on the current branches in the power chips. In the related art, high-precision sampling resistors are generally used to sample the current. The smaller the resistance of the high-precision sampling resistor, the lower the power loss of the current sampling circuit; however, when a high-precision sampling resistor with a small resistance value is used for current sampling, the effective voltage signal on the sampling resistor is also small. The smaller the effective voltage signal, the higher the accuracy requirement for the sampling circuit. Therefore, it is generally necessary to amplify the effective voltage signal, so as to obtain the sampled current value through calculation. The current sampling circuit provided in the current related art currently introduces a large error when performing high-side current sampling, which makes the current sampling accuracy low. Summary of the invention

[0004] The present application provides a current sampling circuit, a chip and an electronic device to solve the technical problem of low current sampling accuracy in the related art.

[0005] In a first aspect, the present application provides a current sampling circuit for sampling a current value on a current branch to be measured, the current sampling circuit comprising: a first sampling branch, a second sampling branch and an operational amplifier;

[0006] The sampling end of the first sampling branch is connected to the first end of the sampling resistor, the output end of the first sampling branch is connected to the first input end of the operational amplifier, and the sampling resistor is connected in series on the current branch to be measured;

[0007] The second sampling branch includes a first resistor, a second resistor and a transistor, wherein the first end of the first resistor is connected to the second end of the sampling resistor, and the second end of the first resistor is connected to the second input end of the operational amplifier; the second end of the first resistor is also connected to the first electrode of the transistor, the second electrode of the transistor is connected to the first end of the second resistor, and the second end of the second resistor is grounded; the control electrode of the transistor is connected to the output end of the operational amplifier; the ratio of the second resistor to the first resistor is the voltage amplification factor;

[0008] The first sampling branch is used to sample a first sampling voltage at the first end of the sampling resistor, and the second sampling branch is used to sample a second sampling voltage at the second end of the sampling resistor, and output the second sampling voltage to the second input end of the operational amplifier; the operational amplifier is used to amplify the difference between the first sampling voltage and the second sampling voltage according to the amplification factor;

[0009] The second pole of the transistor is the first sampling output terminal of the current sampling circuit, and the first sampling output terminal is used to output a first voltage value; the first voltage value is obtained according to the first sampling voltage, the second sampling voltage and the amplification factor, and the first voltage value is used to characterize the current value to be measured on the current branch to be measured.

[0010] In a possible design, the current sampling circuit further includes a sampling control circuit, and the sampling control circuit includes a first switch, a second switch, a third switch and a drive control circuit;

[0011] The control electrode of the transistor is connected to the output terminal of the operational amplifier through the first switch, the second end of the first resistor is connected to the second input terminal of the operational amplifier through the second switch, and the sampling end of the first sampling branch is connected to the first input terminal of the operational amplifier through the third switch;

[0012] The control electrodes of the first switch, the second switch and the third switch are all connected to the drive control circuit, and the drive control circuit is used to output a drive signal to control the conduction or cutoff of the first switch, the second switch and the third switch, thereby controlling the conduction or cutoff of the first sampling branch and the second sampling branch.

[0013] In a possible design, the current sampling circuit further includes a third sampling branch and a fourth sampling branch;

[0014] The third sampling branch includes a third resistor and a fourth resistor, wherein the first end of the third resistor is connected to the first end of the sampling resistor, and the second end of the third resistor is connected to the first input end of the operational amplifier; the second end of the third resistor is also connected to the first end of the fourth resistor, and the second end of the fourth resistor is connected to the output end of the operational amplifier; the ratio of the fourth resistor to the third resistor is the voltage amplification factor;

[0015] The fourth sampling branch includes a fifth resistor and a sixth resistor, the first end of the fifth resistor is connected to the second end of the sampling resistor, the second end of the fifth resistor is connected to the second input end of the operational amplifier, the second end of the fifth resistor is also connected to the first end of the sixth resistor, and the second end of the sixth resistor is grounded; the ratio of the sixth resistor to the fifth resistor is the voltage amplification factor;

[0016] When the first sampling branch and the second sampling branch are disconnected, the third sampling branch is used to sample a third sampling voltage at the first end of the sampling resistor; the fourth sampling branch is used to sample a fourth sampling voltage at the second end of the sampling resistor; the operational amplifier is used to amplify the difference between the third sampling voltage and the fourth sampling voltage according to the voltage amplification factor to obtain a second voltage value, and the second voltage value is used to characterize the current value to be measured on the current branch to be measured.

[0017] In one possible design, the sampling control circuit further includes a fourth switch, a fifth switch and a sixth switch;

[0018] The second end of the fifth resistor is connected to the second input end of the operational amplifier through the fourth switch; the second end of the third resistor is connected to the first input end of the operational amplifier through the fifth switch; the second end of the fourth resistor is connected to the output end of the operational amplifier through the sixth switch;

[0019] The control electrodes of the fourth switch, the fifth switch and the sixth switch are also connected to the drive control circuit, and the drive control circuit is also used to output a drive signal to control the conduction or cutoff of the fourth switch, the fifth switch and the sixth switch, thereby controlling the conduction or cutoff of the third sampling branch and the fourth sampling branch.

[0020] In a possible design, the drive control circuit is used to output a corresponding drive signal to control the first sampling branch and the second sampling branch to be turned on, and to control the third sampling branch and the fourth sampling branch to be turned off in a high-side current sampling scenario;

[0021] And it is used to output a corresponding driving signal to control the first sampling branch and the second sampling branch to be turned off, and to control the third sampling branch and the fourth sampling branch to be turned on in a low-side current sampling scenario.

[0022] In a possible design, the first end of the sampling resistor is connected to the positive electrode of a power supply, and the negative electrode of the power supply is grounded; the second end of the sampling resistor is connected to the output end of a power management chip; the sampling end of the first sampling branch is connected to the first end of the sampling resistor, and the first end of the first resistor in the second sampling branch is connected to the second end of the sampling resistor.

[0023] In a possible design, the first end of the sampling resistor is grounded, the second end of the sampling resistor is connected to the negative electrode of the power supply, and the positive electrode of the power supply is connected to the output end of the power management chip; the first end of the third resistor in the third sampling branch is connected to the first end of the sampling resistor, and the first end of the fifth resistor in the fourth sampling branch is connected to the second end of the sampling resistor.

[0024] In a possible design, in a high-side current sampling scenario, the first voltage value output by the first sampling output terminal is expressed as:

[0025] IBAT_SNS1=K1*K A *I_BAT*R_SNS+50*K A *Vos1 (1)

[0026] In the above formula (1), IBAT_SNS1 is the first voltage value, K1 is the voltage amplification factor, K A is the proportional error coefficient between the first resistor and the second resistor, I_BAT is the current value on the current branch to be measured, Vos1 is the difference between the first sampling voltage and the second sampling voltage, and R_SNS is the resistance value of the sampling resistor.

[0027] In a possible design, in a low-side current sampling scenario, the second voltage value outputted by the output terminal of the operational amplifier is expressed as:

[0028]

[0029] In the above formula (2), IBAT_SNS2 is the second voltage value, K B is the proportional error coefficient between the fourth resistor and the third resistor, Kc is the proportional error coefficient between the sixth resistor and the fifth resistor, K1 is the voltage amplification factor, V OS2 is the difference between the third sampling voltage and the fourth sampling voltage, I_BAT is the current value on the current branch to be measured, R_SNS is the resistance value of the sampling resistor, and V_BAT is the voltage value of the common mode voltage on the current branch to be measured.

[0030] In one possible design, the operational amplifier is a chopper operational amplifier.

[0031] In a second aspect, the present application further provides a chip, which includes a current sampling circuit as described in any one of the above items.

[0032] In a third aspect, the present application further provides an electronic device, which includes the current sampling circuit as described in any one of the above items; or includes the chip as described above.

[0033] The current sampling circuit provided by the first aspect above includes: a first sampling branch, a second sampling branch and an operational amplifier; the sampling end of the first sampling branch is connected to the first end of the sampling resistor, the output end of the first sampling branch is connected to the first input end of the operational amplifier, and the sampling resistor is connected in series on the current branch to be measured; the second sampling branch includes a first resistor, a second resistor and a transistor, the first end of the first resistor is connected to the second end of the sampling resistor, and the second end of the first resistor is connected to the second input end of the operational amplifier; the second end of the first resistor is also connected to the first electrode of the transistor, the second electrode of the transistor is connected to the first end of the second resistor, and the second end of the second resistor is grounded; the control electrode of the transistor is connected to the output end of the operational amplifier; the ratio of the second resistor to the first resistor is the voltage amplification factor; the first sampling branch is used to sample the first sampling voltage of the first end of the sampling resistor, the second sampling branch is used to sample the second sampling voltage of the second end of the sampling resistor, and output the second sampling voltage to the second input end of the operational amplifier; the operational amplifier is used to amplify the difference between the first sampling voltage and the second sampling voltage according to the amplification factor; the second electrode of the transistor is the first sampling output end of the current sampling circuit to output the first voltage value. When the current sampling circuit provided by the present application is used for high-side current sampling, the error caused by the common-mode voltage is eliminated, thereby achieving higher sampling accuracy.

[0034] The beneficial effects provided in the above-mentioned second aspect and various possible designs of the above-mentioned second aspect can refer to the beneficial effects brought about by the above-mentioned first aspect and various possible implementation methods of the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0036] Figure 1 One of the current sampling circuit structure schematic diagrams provided for related technologies;

[0037] Figure 2 The second schematic diagram of the current sampling circuit structure provided for the related technology;

[0038] Figure 3 A schematic diagram showing a sampling voltage output by a current sampling circuit in the related art;

[0039] Figure 4 One of the schematic diagrams of the current sampling circuit structure provided in the embodiment of the present application;

[0040] Figure 5 A schematic diagram of an expression of a first voltage value output by a current sampling circuit provided in an embodiment of the present application;

[0041] Figure 6 The second schematic diagram of the current sampling circuit structure provided in the embodiment of the present application;

[0042] Figure 7 One of the schematic diagrams of the connection relationship between the drive control circuit and each switch provided in the embodiment of the present application;

[0043] Figure 8 The third schematic diagram of the current sampling circuit structure provided in the embodiment of the present application;

[0044] Fig. 9 A second schematic diagram of the connection relationship between the drive control circuit and each switch provided in an embodiment of the present application;

[0045] Fig.10 This is the fourth schematic diagram of the current sampling circuit structure provided in the embodiment of the present application. DETAILED DESCRIPTION

[0046] In this application, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c alone can represent: a, b, c, a and b, a and c, or a, b, and c, where a, b, and c can be single or multiple. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0047] The directions or positional relationships indicated by terms such as "center", "longitudinal", "lateral", "up", "down", "left", "right", "front", and "back" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0048] The terms "connected" and "connected" should be understood in a broad sense. For example, the "connected" or "connected" of a circuit structure can refer to not only physical connection, but also electrical connection or signal connection. For example, it can be directly connected, that is, physically connected, or indirectly connected through at least one intermediate element, as long as the circuit is connected, or it can be the internal connection of two elements; signal connection can refer to signal connection through a circuit or through a media medium, such as radio waves. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0049] The transistor in the present application is a three-terminal transistor, and its three terminals are a control electrode, a first electrode, and a second electrode. The transistor can be a bipolar transistor or a field effect transistor, etc. For example, when the transistor is a bipolar transistor, its control electrode refers to the base of the bipolar transistor, the first electrode can be the collector or emitter of the bipolar transistor, and the corresponding second electrode can be the emitter or collector of the bipolar transistor; when the transistor is a field effect transistor, its control electrode refers to the gate of the field effect transistor, the first electrode can be the drain or source of the field effect transistor, and the corresponding second electrode can be the source or drain of the field effect transistor.

[0050] The power supply on the current branch to be tested in the present application may specifically be a battery. In a typical application scenario, a battery and a power management chip (Power Management IC, referred to as PMIC) are included in the electronic device. For example, existing electronic devices such as mobile phones and tablet computers on the market are equipped with lithium batteries for energy storage, and the output terminal VSYS of the power management chip is connected to the battery. When the power adapter is used to charge the electronic device, the mains power is converted into an adapted direct current through the power adapter, and then input to the power management chip or other auxiliary charging chip through the USB (Universal Serial Bus) charging line, and then enters the battery after passing through the power management chip or other auxiliary charging chip to realize the charging of the battery. Among them, in the process of charging the battery by the power management chip, it generally includes Rapid Charge mode and Trickle Charge mode. Among them, when charging the battery in any charging mode, the current can be set to ensure the safety of battery charging. Among them, the electric energy in the electronic device is provided by the battery, and the battery supplies power to each load in each electronic device after passing through the power management chip.

[0051] In order to ensure the working safety and stability of the circuit system, it is usually necessary to monitor the current value in the circuit in real time, so it is necessary to accurately sample the current value in the circuit. For example, in the related art, the current in the power chip used for charging electronic devices usually requires high-precision sampling and monitoring to ensure the stability and safety of the electronic devices when charging. In the related art, a high-precision sampling resistor is generally used to sample the current. The smaller the resistance of the high-precision sampling resistor, the lower the power loss on the sampling resistor in the current sampling circuit; however, when a high-precision sampling resistor with a smaller resistance value is used for current sampling, the effective voltage signal on the sampling resistor is also smaller, that is, the smaller the effective voltage signal output by the current sampling circuit is, the smaller the output effective voltage signal is, the higher the accuracy requirement of the sampling circuit is, because when the output effective voltage signal is smaller, the error has a greater impact on the output effective voltage signal. Therefore, it is generally necessary to amplify the effective voltage signal at both ends of the sampling resistor, so as to obtain the sampled current value through calculation.

[0052] In the related art, in order to sample the current value on the current branch to be measured in the power chip used to charge the electronic device, a high-precision resistor outside the chip is usually used for current sampling, and the resistance of the high-precision resistor is relatively small. For example, a sampling resistor with a resistance of 10mΩ, 5mΩ, or 2mΩ is usually used for current sampling. Since the resistance of the sampling resistor is relatively small, it is usually necessary to amplify the signal of the voltage difference across the sampling resistor, so as to sample the current value on the current branch to be measured.

[0053] Figure 1 One of the current sampling circuit structure diagrams provided for related technologies, see Figure 1 As shown, taking the current sampling circuit applied to the high-side current circuit as an example, the current branch to be sampled is equivalent to the first current source I_BAT1 and the first power supply V_BAT1 connected in series, and the first sampling resistor R_SNS1 is connected in series between the first current source I_BAT1 and the first power supply V_BAT1, so the current sampling belongs to the high-side current sampling scenario; specifically, the positive electrode of the first current source I_BAT1 is connected to the first end of the first sampling resistor R_SNS1, and the negative electrode of the first current source I_BAT1 is grounded GND. Please continue to refer to Figure 1As shown, the current sampling circuit includes a first sampling resistor R_SNS1, a first proportional resistor RA, a second proportional resistor RA1, a third proportional resistor RB, a fourth proportional resistor RB1 and a first operational amplifier OP1, wherein the first sampling resistor R_SNS1 is connected in series between the first current source I_BAT1 and the first power source V_BAT1, the first end of the third proportional resistor RB is connected to the first end of the first sampling resistor R_SNS1, and the second end of the third proportional resistor RB is connected to the inverting input end of the first operational amplifier OP1; at the same time, the second end of the third proportional resistor RB is also connected to the first end of the fourth proportional resistor RB1, and the second end of the fourth proportional resistor RB1 is connected to the output end of the first operational amplifier OP1; wherein the first end of the first proportional resistor RA is connected to the second end of the first sampling resistor R_SNS1, the second end of the first proportional resistor RA is connected to the non-inverting input end of the first operational amplifier OP1, the second end of the first proportional resistor RA is also connected to the first end of the second proportional resistor RA1, and the second end of the second proportional resistor RA1 is grounded GND. The output end of the first operational amplifier OP1 is the output end of the current sampling circuit and is used for the amplified voltage signal. The current value of the first current source I_BAT1 can be calculated according to the voltage signal and the resistance value of the first sampling resistor R_SNS1.

[0054] in, Figure 1 When the current sampling circuit shown is working, the current I_BAT1 output by the first current source I_BAT1 generates a voltage drop after passing through the first sampling resistor R_SNS1, and then the voltage drop is amplified by the first operational amplifier OP1 and output; wherein, the amplification factor of the voltage drop is determined by the ratio between the first proportional resistor RA and the second proportional resistor RA1, or the amplification factor of the voltage drop is determined by the ratio between the third proportional resistor RB and the fourth proportional resistor RB1, and generally, the ratio between the first proportional resistor RA and the second proportional resistor RA1 is the same as the ratio between the third proportional resistor RB and the fourth proportional resistor RB1.

[0055] In actual application scenarios, due to certain process deviations in the production of various components in the current sampling circuit, there is a certain deviation between the actual ratio and the theoretical ratio of the first proportional resistor RA and the second proportional resistor RA1. At the same time, there is a certain deviation between the actual ratio and the theoretical ratio of the third proportional resistor RB and the fourth proportional resistor RB1, which affects the output result of the final first operational amplifier OP1, that is, affects the final current sampling accuracy.

[0056] In this embodiment, the magnification ratio is 50 times. Figure 1Assume that due to the error generated by each device during production, the proportional error coefficient between the first proportional resistor RA and the second proportional resistor RA1 in this embodiment is K D The proportional error coefficient between the third proportional resistor RB and the fourth proportional resistor RB1 is K E , according to the amplification factor and proportional error coefficient K between the first proportional resistor RA and the second proportional resistor RA1 D , then the second proportional resistor RA1 can be expressed as 50*K D *RA; Similarly, according to the amplification factor and proportional error coefficient K between the third proportional resistor RB and the fourth proportional resistor RB1 E , then the fourth proportional resistor RB1 can be expressed as 50*K E *RB. At the same time, the voltage drop across the first operational amplifier OP1 can be expressed as V OS , that is, the voltage difference between the first end and the second end of the first sampling resistor R_SNS1 can be expressed as V OS ,but Figure 1 The current sampling circuit shown can be equivalently transformed into Figure 2 As shown, Figure 2 The second schematic diagram of the current sampling circuit structure provided for related technologies is shown in Figure 2 As shown, according to the principle of virtual short and virtual break, Figure 2 The sampling voltage finally output by the current sampling circuit shown is expressed as:

[0057]

[0058] In the above formula, IBAT_SNSO represents the sampling voltage finally output by the first operational amplifier OP1, 50 is the amplification factor designed for the current sampling circuit, and K D is the proportional error coefficient between the first proportional resistor RA and the second proportional resistor RA1, K E is the proportional error coefficient between the third proportional resistor RB and the fourth proportional resistor RB1, I_BAT1 is the current value of the first current source I_BAT1 to be sampled, R_SNS1 is the resistance value of the first sampling resistor R_SNS1, V_BAT1 is the voltage value of the first power supply input in common mode, V OS is the voltage difference between the first end and the second end of the first sampling resistor R_SNS1.

[0059] It can be understood that, without considering the error caused by the production of electronic devices, the proportional error coefficient K between the first proportional resistor RA and the second proportional resistor RA1 is D is 1. Similarly, the proportional error coefficient K between the third proportional resistor RB and the fourth proportional resistor RB1 EThe error ratio of the common device in the prior art is one thousandth (1‰). Therefore, the proportional error coefficient K in this embodiment is E and K D The value can be 0.9999. In addition, in order to improve the sampling accuracy, the equivalent input error of the first operational amplifier OP1 generally used is small, that is, the voltage difference V between the first end and the second end of the first sampling resistor R_SNS1 in this embodiment is OS The value is relatively small. Generally, according to the experience of those skilled in the art, the voltage difference V between the first end and the second end of the first sampling resistor R_SNS1 is OS The value can be 100uV.

[0060] Figure 3 This is a schematic diagram showing the sampling voltage output by the current sampling circuit in the related art, see Figure 3 As shown, the expression of the sampling voltage finally output by the current sampling circuit mainly includes three parts. The first part is the error caused by the operational amplifier, the second part is the sampling voltage amplified by the operational amplifier, and the second part is also the essential core of the sampling voltage. The third part is the error caused by the amplified industrial mode voltage.

[0061] Among them, the pressure difference V in the first part OS The second part is the core part of the sampled voltage. The mismatch of the amplification ratio of the two pairs of resistors will affect the sampling accuracy of this part. However, since the error caused by the general proportional error coefficient is one thousandth, the error caused by the second part can usually be approximated to one thousandth. Therefore, the impact of this part of the error on the sampling accuracy can be ignored. In the third part, since 1 and Figure 2 The current sampling circuit shown is a high-side current sampling circuit, so the common-mode input voltage V_BAT1 provided by the first voltage source will have a greater impact. For example, in most power chips, the common-mode input voltage V_BAT1 provided by the first voltage source is usually around 4V, so this part will bring a voltage error at the mV level, specifically about 4mV. For example, taking the first sampling resistor R_SNS1 with a resistance of 10mΩ and an amplification factor of 50 as an example, the sampling output corresponding to the 100mA circuit branch is 50mV, then the error caused by the common-mode voltage of the third part is about 4mV, which makes the overall current sampling accuracy error about 8%. In the low-side current sampling scenario, the common-mode input voltage V_BAT1 is usually 0V, so the third part will not bring any error impact.

[0062] It can be seen from this that Figure 1When the current sampling circuit provided in the related technology shown is applied in the scenario of high-side current sampling, the common-mode voltage will inevitably be amplified, introducing a large sampling error. In particular, the sampling accuracy will be greatly affected when the current is small, resulting in a large error in the current sampling result, which is difficult to apply to most current sampling scenarios with high accuracy requirements.

[0063] In order to overcome the defects in the above-mentioned related technologies, the present application provides a current sampling circuit, including: a first sampling branch, a second sampling branch and an operational amplifier; the sampling end of the first sampling branch is connected to the first end of the sampling resistor, the output end of the first sampling branch is connected to the first input end of the operational amplifier, and the sampling resistor is connected in series on the current branch to be measured; the second sampling branch includes a first resistor, a second resistor and a transistor, the first end of the first resistor is connected to the second end of the sampling resistor, and the second end of the first resistor is connected to the second input end of the operational amplifier; the second end of the first resistor is also connected to the first electrode of the transistor, the second electrode of the transistor is connected to the first end of the second resistor, and the second end of the second resistor is grounded; the control electrode of the transistor is connected to the output end of the operational amplifier; the ratio of the second resistor to the first resistor is a voltage amplification factor; the first sampling branch is used to sample a first sampling voltage at the first end of the sampling resistor, the second sampling branch is used to sample a second sampling voltage at the second end of the sampling resistor, and output the second sampling voltage to the second input end of the operational amplifier; the operational amplifier is used to amplify the difference between the first sampling voltage and the second sampling voltage according to the amplification factor; the second electrode of the transistor is the first sampling output end of the current sampling circuit to output a first voltage value. When the current sampling circuit provided by the present application is used for high-side current sampling, the error caused by the common-mode voltage is eliminated, thereby achieving higher sampling accuracy.

[0064] Figure 4 One of the current sampling circuit structure diagrams provided in the embodiment of the present application is shown in FIG. Figure 4As shown, the current sampling circuit includes: a first sampling branch 10, a second sampling branch 20 and an operational amplifier OP. The sampling end of the first sampling branch 10 is connected to the first end of the sampling resistor R_SNS, and the output end of the first sampling branch 10 is connected to the first input end of the operational amplifier OP. Among them, the sampling resistor R_SNS is connected in series on the current branch to be measured, and the branch to be measured is also provided with a current source I_BAT and a power supply V_BAT, and the sampling resistor R_SNS is connected in series between the current source I_BAT and the power supply V_BAT. The second sampling branch 20 includes a first resistor R1, a second resistor R2 and a transistor Q1, the first end of the first resistor R1 is connected to the second end of the sampling resistor R_SNS, and the second end of the first resistor R1 is connected to the second input end of the operational amplifier OP; the second end of the first resistor R1 is also connected to the first electrode of the transistor Q1, the second electrode of the transistor Q1 is connected to the first end of the second resistor R2, and the second end of the second resistor R2 is grounded GND; the control electrode of the transistor Q1 is connected to the output end of the operational amplifier OP; the ratio of the second resistor R2 to the first resistor R1 is the voltage gain K1. Among them, the first sampling branch 10 is used to sample the first sampling voltage of the first end of the sampling resistor R_SNS, and output the first sampling voltage to the first input end of the operational amplifier, and the second sampling branch 20 is used to sample the second sampling voltage of the second end of the sampling resistor R_SNS, and output the second sampling voltage to the second input end of the operational amplifier; the operational amplifier OP is used to amplify the difference between the first sampling voltage and the second sampling voltage according to the amplification factor K1; the second pole of the transistor Q1 is the first sampling output end of the current sampling circuit to output the first voltage value IBAT_SNS1.

[0065] See also Figure 4 As shown, in one embodiment, the first end of the sampling resistor R_SNS is connected to the positive electrode of the power supply V_BAT, and the negative electrode of the power supply V_BAT is grounded GND; the second end of the sampling resistor R_SNS is connected to the output end VSYS of the power management chip. It can be understood that the output end VSYS of the power management chip is used to output a stable power supply current, which is equivalent to the above-mentioned current source I_BAT can output a stable power supply current. Among them, the sampling end of the first sampling branch 10 is connected to the first end of the sampling resistor R_SNS, and the first end of the first resistor R1 in the second sampling branch 20 is connected to the second end of the sampling resistor R_SNS. In this way, the current sampling circuit provided according to this embodiment can accurately sample the high-side current.

[0066] right Figure 4 It can be seen from the analysis of the current sampling circuit shown that in the high-side current sampling scenario, the first voltage value output by the first sampling output terminal is expressed as:

[0067] IBAT_SNS1=K1*K A*I_BAT*R_SNS+50*K A *Vos1 (1)

[0068] In the above formula (1), IBAT_SNS1 is the first voltage value output by the first sampling output terminal, K1 is the voltage amplification factor in this embodiment, and K A is the proportional error coefficient of the first resistor R1 and the second resistor R2, I_BAT is the current value on the current branch to be measured, Vos1 is the difference between the first sampling voltage and the second sampling voltage, and R_SNS is the resistance value of the sampling resistor R_SNS.

[0069] Wherein, K1 is the ratio of the second resistor R2 to the first resistor R1. In this embodiment, K1=50, and the proportional error coefficient is 0.9999, that is, R2=K1*K A *R1, the common mode voltage of the power supply V_BAT input is 4V, and the difference between the first sampling voltage and the second sampling voltage Vos1 is 100uV. For example, the sampling error is analyzed and explained.

[0070] The above formula (1) can be expressed as Figure 5 The expression shown, Figure 5 For a schematic diagram of an expression of a first voltage value output by a current sampling circuit provided in an embodiment of the present application, see Figure 5 As shown, the expression of the first voltage value IBAT_SNS1 is mainly composed of two parts, wherein the first part is the error caused by the operational amplifier, and the second part is the amplified sampling voltage, which is the core part of the first voltage value IBAT_SNS1 in this embodiment. The first part is equivalent to 50 times the equivalent input of the operational amplifier. Since the equivalent input Vos1 of the operational amplifier is at the uV level, the error introduced by the first part is less than 1mV; the error introduced in the second part is caused by the imbalance of the first resistor R1 and the second resistor R2. Through the above analysis, it can be seen that the error caused by this part is usually one thousandth, which can be ignored.

[0071] By comparing the sampling voltage output by the current sampling circuit in the above-mentioned related art, it can be known that according to the current sampling circuit provided in this embodiment, when the current sampling circuit is applied to high-side current sampling, the first voltage value IBAT_SNS1 outputted by the current sampling circuit eliminates the third part that introduces a large error in the related art, that is, eliminates the error caused by the common mode voltage, so that the sampling accuracy is greatly improved.

[0072] Figure 6 For the second schematic diagram of the current sampling circuit structure provided in the embodiment of the present application, please refer to Figure 6As shown, in some embodiments, the current sampling circuit further includes a sampling control circuit 50 , which includes a first switch S1 , a second switch S2 , a third switch S3 and a driving control circuit 60 .

[0073] Among them, the control electrode of the transistor Q1 is connected to the output end of the operational amplifier OP through the first switch S1, that is, the first switch S1 is connected in series between the control electrode of the transistor Q1 and the output end of the operational amplifier OP; the second end of the first resistor R1 is connected to the second input end of the operational amplifier OP through the second switch S2, that is, the second switch S2 is connected in series between the second end of the first resistor R1 and the second input end of the operational amplifier OP; the sampling end of the first sampling branch 10 is connected to the first input end of the operational amplifier OP through the third switch S3, that is, the third switch S3 is connected in series between the sampling end of the first sampling branch 10 and the first input end of the operational amplifier OP.

[0074] Figure 7 This is a schematic diagram of the connection relationship between the drive control circuit and each switch provided in the embodiment of the present application. Figure 7 As shown, the control electrodes of the first switch S1, the second switch S2 and the third switch S3 are all connected to the drive control circuit 60, and the drive control circuit 60 is used to output a drive signal to control the conduction or cutoff of the first switch S1, the second switch S2 and the third switch S3, thereby controlling the conduction or cutoff of the first sampling branch 10 and the second sampling branch 20.

[0075] It is understandable that based on Figure 6 In the current sampling circuit shown, when the first switch S1 and the second switch S2 are closed, the sampling terminal CSP of the first sampling branch 10 is connected to the second end of the sampling resistor R_SNS to sample the second sampling voltage of the second end of the sampling resistor R_SNS. When the third switch S3 is closed, the sampling terminal CSN of the second sampling branch 20 is connected to the first end of the sampling resistor R_SNS to sample the first sampling voltage of the first end of the sampling resistor R_SNS. In addition, the drive control circuit 60 can control whether the current sampling circuit works by controlling the first switch S1, the second switch S2 and the third switch S3 to be turned on or off.

[0076] Figure 8 The third schematic diagram of the current sampling circuit structure provided in the embodiment of the present application is shown in FIG. Figure 8 As shown, the current sampling circuit further includes a third sampling branch 30 and a fourth sampling branch 40 .

[0077] Among them, the third sampling branch 30 includes a third resistor R3 and a fourth resistor R4, the first end of the third resistor R3 is connected to the first end of the sampling resistor R_SNS, and the second end of the third resistor R3 is connected to the first input end of the operational amplifier OP; the second end of the third resistor R3 is also connected to the first end of the fourth resistor R4, and the second end of the fourth resistor R4 is connected to the output end of the operational amplifier OP; the ratio of the fourth resistor R4 to the third resistor R3 is the voltage amplification factor K1.

[0078] Among them, the fourth sampling branch 40 includes a fifth resistor R5 and a sixth resistor R6, the first end of the fifth resistor R5 is connected to the second end of the sampling resistor R_SNS, the second end of the fifth resistor R5 is connected to the second input end of the operational amplifier OP, the second end of the fifth resistor R5 is also connected to the first end of the sixth resistor R6, and the second end of the sixth resistor R6 is grounded GND; the ratio of the sixth resistor R6 to the fifth resistor R5 is the voltage amplification factor K1.

[0079] When the first sampling branch 10 and the second sampling branch 20 are disconnected, the third sampling branch 30 is used to sample the third sampling voltage at the first end of the sampling resistor R_SNS, and the fourth sampling branch 40 is used to sample the fourth sampling voltage at the second end of the sampling resistor R_SNS; the operational amplifier OP is used to obtain the difference V between the third sampling voltage and the fourth sampling voltage according to the voltage amplification factor K1. OS2 Amplification is performed to obtain a second voltage value, where the second voltage value is used to characterize the current value I_BAT to be measured on the current branch to be measured.

[0080] according to Figure 8 According to the current sampling circuit shown in FIG. 1 , the second voltage value IBAT_SNS2 outputted from the output terminal of the operational amplifier OP is analyzed, and it can be seen that the second voltage value can be expressed as:

[0081]

[0082] In the above formula (2), IBAT_SNS2 is the second voltage value output by the operational amplifier OP, K B is the proportional error coefficient of the fourth resistor R4 and the third resistor R3, Kc is the proportional error coefficient of the sixth resistor R6 and the fifth resistor R5, K1 is the voltage amplification factor, specifically the resistance ratio of the sixth resistor R6 and the fifth resistor R5, or the resistance ratio of the fourth resistor R4 and the third resistor R3; V OS2 is the difference between the third sampling voltage and the fourth sampling voltage, I_BAT is the current value on the current branch to be measured, R_SNS is the resistance value of the sampling resistor, and V_BAT is the voltage value of the common mode voltage on the current branch to be measured.

[0083] It can be understood that, without considering the error caused by the production of electronic components, the proportional error coefficient K of the fourth resistor R4 and the third resistor R3 is B is 1. Similarly, the proportional error coefficient K of the sixth resistor R6 and the fifth resistor R5 C Also 1.

[0084] In one embodiment, the operational amplifier OP is a chopper operational amplifier, so the voltage difference between the two input ends of the operational amplifier OP is 100 uV.

[0085] According to the above description, the second voltage value shown in formula (2) mainly includes three parts. The first part is the error caused by the operational amplifier, the second part is the sampling voltage amplified by the operational amplifier, and the second part is also the essential core of the sampling voltage. The third part is the error caused by the amplified working mode voltage. According to the above analysis, the errors caused by the first and second parts are small and can be ignored. It is mainly the third part that will introduce a large measurement error.

[0086] By analyzing the above formula (2), it can be seen that in the high-side current sampling scenario, due to the existence of the power supply I_BAT, the common-mode input voltage is V_BAT, and the common-mode input voltage V_BAT is amplified by K1 times, which is easy to introduce large error interference. At this time, the current sampling circuit is equivalent to Figure 1 The current sampling circuit shown in the figure results in low current sampling accuracy. In the low-side current sampling scenario, since the common-mode input voltage V_BAT can be considered as 0V, the large error interference caused by this item is eliminated and the current sampling accuracy is not affected.

[0087] Therefore, please combine Figure 8 As shown, in the low-side current sampling scenario, when the first switch S1, the second switch S2 and the third switch S3 are all controlled to be open, that is, the first sampling branch 10 and the second sampling branch 20 are both in the disconnected state, the third sampling branch 30 and the fourth sampling branch 40 work, and the current value on the current branch to be measured can be accurately sampled.

[0088] Please continue to see Figure 8As shown, in one embodiment, the sampling control circuit 50 in the current sampling circuit further includes a fourth switch S4, a fifth switch S5 and a sixth switch S6; the second end of the fifth resistor R5 is connected to the second input end of the operational amplifier OP through the fourth switch S4, that is, the fourth switch S4 is connected in series between the second end of the fifth resistor R5 and the second input end of the operational amplifier OP; the second end of the third resistor R3 is connected to the first input end of the operational amplifier OP through the fifth switch S5, that is, the fifth switch S5 is connected in series between the second end of the third resistor R3 and the first input end of the operational amplifier OP; the second end of the fourth resistor R4 is connected to the output end of the operational amplifier OP through the sixth switch S6, that is, the sixth switch S6 is connected in series between the second end of the fourth resistor R4 and the output end of the operational amplifier OP.

[0089] It should be noted that in the embodiment of the present application, the first input terminal of the operational amplifier OP is the inverting input terminal, and the second input terminal of the operational amplifier OP is the non-inverting input terminal. In other embodiments, the first input terminal of the operational amplifier OP can also be the non-inverting input terminal, and the second input terminal of the operational amplifier OP can be the inverting input terminal.

[0090] Among them, this embodiment Figure 4 and Figure 8 The transistor Q1 in the embodiment adopts an NMOS (N-Metal-Oxide-Semiconductor) tube. In other embodiments, the transistor Q1 may also adopt a PMOS (P-Metal-Oxide-Semiconductor) tube. For example, when the transistor Q1 adopts an NMOS tube, its first electrode is a drain electrode, the second electrode is a source electrode, and the control electrode is a gate electrode.

[0091] Fig. 9 For the second schematic diagram of the connection relationship between the drive control circuit and each switch provided in the embodiment of the present application, please refer to Fig. 9 As shown, the control electrodes of the fourth switch S4, the fifth switch S5 and the sixth switch S6 are also connected to the drive control circuit 60. The drive control circuit 60 is also used to output a drive signal to control the conduction or cutoff of the fourth switch S4, the fifth switch S5 and the sixth switch S6, thereby controlling the conduction or cutoff of the third sampling branch 30 and the fourth sampling branch 40.

[0092] Among them, the drive control circuit 60 in this embodiment is used to output the corresponding drive signal to control the first sampling branch 10 and the second sampling branch 20 to be turned on, and to control the third sampling branch 30 and the fourth sampling branch 40 to be turned off in the high-side current sampling scenario; specifically, the drive control circuit 60 is used to output the corresponding drive signal to control the first switch S1, the second switch S2 and the third switch S3 to be turned on, and to control the fourth switch S4, the fifth switch S5 and the sixth switch S6 to be turned off in the high-side current sampling scenario, so as to realize the above-mentioned first sampling branch 10 and the second sampling branch 20 to be turned on, and the third sampling branch 30 and the fourth sampling branch 40 to be turned off, thereby adopting the following method: Figure 4 The current sampling circuit shown realizes accurate current sampling of the high-side current circuit.

[0093] The drive control circuit 60 in this embodiment is also used to output a corresponding drive signal to control the first sampling branch 10 and the second sampling branch 20 to be turned off, and to control the third sampling branch 30 and the fourth sampling branch 40 to be turned on in the low-side current sampling scenario. Specifically, the drive control circuit 60 is used to output a corresponding drive signal to control the first switch S1, the second switch S2, and the third switch S3 to be turned off, and to control the fourth switch S4, the fifth switch S5, and the sixth switch S6 to be turned on in the high-side current sampling scenario, so as to realize the above-mentioned first sampling branch 10 and the second sampling branch 20 to be turned off, and the third sampling branch 30 and the fourth sampling branch 40 to be turned on, so as to adopt the above-mentioned Figure 8 The current sampling circuit shown realizes accurate current sampling of the low-side current circuit.

[0094] Fig.10 The fourth schematic diagram of the current sampling circuit structure provided in the embodiment of the present application is shown in FIG. Fig.10 As shown, in one embodiment, the first end of the sampling resistor R_SNS is grounded GND, the second end of the sampling resistor R_SNS is connected to the negative electrode of the power supply V_BAT, the positive electrode of the power supply V_BAT is connected to the output end YSVS of the power management chip, and the output end VSYS of the power management chip is used to output a stable power supply current, which is equivalent to the above-mentioned current source I_BAT can output a stable power supply current. The first end of the third resistor R3 in the third sampling branch 30 is connected to the first end of the sampling resistor R_SNS, and the first end of the fifth resistor R5 in the fourth sampling branch 40 is connected to the second end of the sampling resistor R_SNS. In this way, the current sampling circuit provided according to this embodiment can accurately sample the low-side current.

[0095] It can be seen that by adopting the current sampling circuit provided in this embodiment, the operation of different sampling branches can be controlled by controlling the on and off of each switch in the circuit according to the use scenario of the circuit, so that the circuit is suitable for high-side current sampling and low-side current sampling, and both can ensure high sampling accuracy, and the use scenarios are more extensive.

[0096] The present application also provides a chip including the current sampling circuit described above. It is understandable that the current sampling circuit described above can be integrated into a circuit chip, or integrated into a power chip, so as to sample and monitor the current of the power chip.

[0097] An embodiment of the present application further provides an electronic device, which includes the current sampling circuit as described above; or the electronic device includes the chip as described above.

[0098] Finally, it should be noted that the above embodiments are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A current sampling circuit for sampling the current value on a current branch to be measured, characterized in that: The current sampling circuit comprises: a first sampling branch, a second sampling branch and an operational amplifier; The sampling end of the first sampling branch is connected to the first end of the sampling resistor, the output end of the first sampling branch is connected to the first input end of the operational amplifier, and the sampling resistor is connected in series on the current branch to be measured; The second sampling branch includes a first resistor, a second resistor and a transistor, wherein the first end of the first resistor is connected to the second end of the sampling resistor, and the second end of the first resistor is connected to the second input end of the operational amplifier; the second end of the first resistor is also connected to the first electrode of the transistor, the second electrode of the transistor is connected to the first end of the second resistor, and the second end of the second resistor is grounded; the control electrode of the transistor is connected to the output end of the operational amplifier; the ratio of the second resistor to the first resistor is the voltage amplification factor; The first sampling branch is used to sample a first sampling voltage at the first end of the sampling resistor, and the second sampling branch is used to sample a second sampling voltage at the second end of the sampling resistor, and output the second sampling voltage to the second input end of the operational amplifier; the operational amplifier is used to amplify the difference between the first sampling voltage and the second sampling voltage according to the amplification factor; The second pole of the transistor is the first sampling output terminal of the current sampling circuit, and the first sampling output terminal is used to output a first voltage value; the first voltage value is obtained according to the first sampling voltage, the second sampling voltage and the amplification factor, and the first voltage value is used to characterize the current value to be measured on the current branch to be measured.

2. The current sampling circuit according to claim 1, characterized in that: The current sampling circuit further includes a sampling control circuit, and the sampling control circuit includes a first switch, a second switch, a third switch and a drive control circuit; The control electrode of the transistor is connected to the output terminal of the operational amplifier through the first switch, the second end of the first resistor is connected to the second input terminal of the operational amplifier through the second switch, and the sampling end of the first sampling branch is connected to the first input terminal of the operational amplifier through the third switch; The control electrodes of the first switch, the second switch and the third switch are all connected to the drive control circuit, and the drive control circuit is used to output a drive signal to control the conduction or cutoff of the first switch, the second switch and the third switch, thereby controlling the conduction or cutoff of the first sampling branch and the second sampling branch.

3. The current sampling circuit according to claim 2, characterized in that: The current sampling circuit also includes a third sampling branch and a fourth sampling branch; The third sampling branch includes a third resistor and a fourth resistor, wherein the first end of the third resistor is connected to the first end of the sampling resistor, and the second end of the third resistor is connected to the first input end of the operational amplifier; the second end of the third resistor is also connected to the first end of the fourth resistor, and the second end of the fourth resistor is connected to the output end of the operational amplifier; the ratio of the fourth resistor to the third resistor is the voltage amplification factor; The fourth sampling branch includes a fifth resistor and a sixth resistor, the first end of the fifth resistor is connected to the second end of the sampling resistor, the second end of the fifth resistor is connected to the second input end of the operational amplifier, the second end of the fifth resistor is also connected to the first end of the sixth resistor, and the second end of the sixth resistor is grounded; the ratio of the sixth resistor to the fifth resistor is the voltage amplification factor; When the first sampling branch and the second sampling branch are disconnected, the third sampling branch is used to sample a third sampling voltage at the first end of the sampling resistor; the fourth sampling branch is used to sample a fourth sampling voltage at the second end of the sampling resistor; the operational amplifier is used to amplify the difference between the third sampling voltage and the fourth sampling voltage according to the voltage amplification factor to obtain a second voltage value, and the second voltage value is used to characterize the current value to be measured on the current branch to be measured.

4. The current sampling circuit according to claim 3, characterized in that: The sampling control circuit further includes a fourth switch, a fifth switch and a sixth switch; The second end of the fifth resistor is connected to the second input end of the operational amplifier through the fourth switch; the second end of the third resistor is connected to the first input end of the operational amplifier through the fifth switch; the second end of the fourth resistor is connected to the output end of the operational amplifier through the sixth switch; The control electrodes of the fourth switch, the fifth switch and the sixth switch are also connected to the drive control circuit, and the drive control circuit is also used to output a drive signal to control the conduction or cutoff of the fourth switch, the fifth switch and the sixth switch, thereby controlling the conduction or cutoff of the third sampling branch and the fourth sampling branch.

5. The current sampling circuit according to claim 4, characterized in that: The drive control circuit is used to output a corresponding drive signal to control the first sampling branch and the second sampling branch to be turned on, and to control the third sampling branch and the fourth sampling branch to be turned off in a high-side current sampling scenario; And it is used to output a corresponding driving signal to control the first sampling branch and the second sampling branch to be turned off, and to control the third sampling branch and the fourth sampling branch to be turned on in a low-side current sampling scenario.

6. The current sampling circuit according to any one of claims 1 to 5, characterized in that: The first end of the sampling resistor is connected to the positive electrode of the power supply, and the negative electrode of the power supply is grounded; the second end of the sampling resistor is connected to the output end of the power management chip; the sampling end of the first sampling branch is connected to the first end of the sampling resistor, and the first end of the first resistor in the second sampling branch is connected to the second end of the sampling resistor.

7. The current sampling circuit according to any one of claims 3 to 5, characterized in that: The first end of the sampling resistor is grounded, the second end of the sampling resistor is connected to the negative electrode of the power supply, and the positive electrode of the power supply is connected to the output end of the power management chip; the first end of the third resistor in the third sampling branch is connected to the first end of the sampling resistor, and the first end of the fifth resistor in the fourth sampling branch is connected to the second end of the sampling resistor.

8. The current sampling circuit according to any one of claims 1 to 5, characterized in that: The operational amplifier is a chopper operational amplifier.

9. A chip, characterized in that: The invention comprises a current sampling circuit as described in any one of claims 1 to 8.

10. An electronic device, characterized in that: Includes the current sampling circuit as described in any one of claims 1 to 8; or includes the chip as described in claim 9.

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