Current sampling circuit for high-side switch driving circuit, chip and electronic equipment

Abstract

The invention relates to the technical field of switch driving, in particular to a current sampling circuit for a high-side switch driving circuit, a chip and electronic equipment. The current sampling circuit comprises a second transistor, a third transistor, an operational amplifier and a voltage clamping circuit. The operational amplifier is used for working in a linear amplification state, so that the second electrode of the high-side switching tube and the second electrode of the second transistor are in a virtual short state; the voltage clamping circuit is used for collecting a first voltage on a second pole of the high-side switching tube and outputting a voltage clamping signal when the first voltage is greater than a preset second voltage; and the voltage clamping signal is used for clamping the voltage difference between the first pole and the second pole of the high-side switching tube to a preset third voltage. In this way, when the load current of the branch where the high-side switching tube is located is small, the offset voltage and the third voltage can be ignored compared, so that the influence of the offset voltage on the load current is reduced, and the sampling precision of the load current is guaranteed.

Description

Technical Field

[0001] The present application relates to the field of switch driving technology, and in particular to a current sampling circuit, a chip and an electronic device for a high-side switch driving circuit. Background Art

[0002] During the operation of the high-side switch driving circuit, it is usually necessary to monitor the current on the target transistor in the circuit in real time to determine whether the high-side switch driving circuit is operating in a normal state.

[0003] In the related art, when monitoring the current on the target transistor in the high-side switch driving circuit, a sampling transistor and an operational amplifier feedback loop are used to form a current sampling circuit, and the current of the branch where the sampling transistor is located is collected, so as to calculate the current value of the branch where the target transistor is located according to the size ratio of the target transistor and the sampling transistor, so as to realize the monitoring of the current value on the target transistor. However, since the operational amplifier feedback loop usually introduces an offset voltage, the current value of the branch where the sampling transistor is located and the current of the branch where the target transistor is located are not completely in the current mirror ratio, but there will be a certain error, so that the current sampling accuracy of the branch where the target transistor is located is low. Summary of the invention

[0004] The present application provides a current sampling circuit, a chip and an electronic device for a high-side switch driving circuit, which aims to solve the technical problem of low current sampling accuracy of a branch where a target transistor is located in the related art.

[0005] In a first aspect, the present application provides a current sampling circuit for a high-side switch driving circuit, comprising: a high-side switch tube, a second transistor, a third transistor, an operational amplifier, a sampling resistor, and a voltage clamping circuit;

[0006] Wherein, the first electrode of the high-side switch tube is connected to the power supply, the second electrode of the high-side switch tube is connected to the first end of the load, and the second end of the load is grounded; the first electrode of the second transistor is also connected to the power supply, the second electrode of the second transistor is connected to the first electrode of the third transistor, the second electrode of the third transistor is connected to the first end of the sampling resistor, and the second end of the sampling resistor is grounded; the control electrode of the high-side switch tube is connected to the control electrode of the second transistor;

[0007] The second electrode of the high-side switch is connected to the non-inverting input terminal of the operational amplifier, the second electrode of the second transistor is connected to the inverting input terminal of the operational amplifier, and the output terminal of the operational amplifier is connected to the control electrode of the third transistor; the operational amplifier is used to work in a linear amplification state so that the second electrode of the high-side switch and the second electrode of the second transistor are in a virtual short state;

[0008] The input end of the voltage clamping circuit is connected to the second pole of the high-side switch tube, and the output end of the voltage clamping circuit is respectively connected to the control pole of the high-side switch tube and the control pole of the second transistor; the voltage clamping circuit is used to collect the first voltage on the second pole of the high-side switch tube, and output a voltage clamping signal when the first voltage is greater than a preset second voltage; the voltage clamping signal is used to clamp the voltage difference between the first pole and the second pole of the high-side switch tube to a preset third voltage.

[0009] In one possible design, the voltage clamp circuit includes a transconductance operational amplifier and a transistor drive circuit;

[0010] The non-inverting input terminal of the transconductance operational amplifier is connected to the input terminal of the voltage clamp circuit, and is used to collect the first voltage on the second electrode of the high-side switch tube; the inverting input terminal of the transconductance operational amplifier is used to receive the preset second voltage; the transconductance operational amplifier is used to output a first current signal when it is determined that the voltage difference between the first voltage and the second voltage is greater than zero;

[0011] The transistor driving circuit is used to generate the voltage clamping signal under the triggering of the first current signal, so as to clamp the voltage difference between the first electrode and the second electrode of the high-side switch tube to a preset third voltage.

[0012] In one possible design, the output end of the transconductance operational amplifier is connected to the input end of the transistor driving circuit, and the input end of the transistor driving circuit is used to receive the output first current signal; the output end of the transistor driving circuit is the output end of the voltage clamping circuit, and the output of the transistor driving circuit is respectively connected to the control electrode of the high-side switch tube and the control electrode of the second transistor.

[0013] In a possible design, the voltage clamping signal is a second current signal; the second current signal is used to control the voltage difference between the control electrode and the second electrode of the high-side switch tube to be reduced to a fourth voltage.

[0014] In a possible design, the first end of the sampling resistor is a voltage sampling end, and the voltage sampling end is used to sample a sampling voltage value on the first end of the sampling resistor.

[0015] In one possible design, the current sampling circuit for the high-side switch driving circuit further includes a sampling current calculation circuit;

[0016] The input end of the sampling current calculation circuit is connected to the voltage sampling end for obtaining the sampling voltage value; the sampling current calculation circuit is used to calculate the load current value of the loop where the load is located according to the sampling voltage value, the resistance value of the sampling resistor, the size ratio of the high-side switch tube and the second transistor, the on-resistance of the second transistor and the offset voltage of the operational amplifier.

[0017] In a possible design, the load current value of the loop where the load is located is calculated according to the sampled voltage value, the resistance value of the sampling resistor, the size ratio of the high-side switch tube and the second transistor, the on-resistance of the second transistor, and the offset voltage of the operational amplifier, including:

[0018] The load current value of the circuit where the load is located is calculated according to the following formula (1):

[0019] Iload=K*(Isns-Vos / Rds2) (1)

[0020] In the above formula (1), Iload is the load current value, K is the size ratio of the high-side switch tube and the second transistor, Isns is the current value calculated based on the sampled voltage value and the sampling resistor, and Rds2 is the on-resistance of the second transistor.

[0021] In a second aspect, the present application further provides a high-side switch driving circuit, which includes the current sampling circuit as described above.

[0022] In a third aspect, the present application further provides a chip, which includes a current sampling circuit as described in any one of the above items.

[0023] In a fourth 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.

[0024] The current sampling circuit provided by the first aspect above includes: a high-side switch tube, a second transistor, a third transistor, an operational amplifier, a sampling resistor and a voltage clamping circuit; wherein the first electrode of the high-side switch tube is connected to a power supply, the second electrode of the high-side switch tube is connected to a first end of a load, and the second end of the load is grounded; the first electrode of the second transistor is also connected to the power supply, the second electrode of the second transistor is connected to a first electrode of a third transistor, the second electrode of the third transistor is connected to a first end of the sampling resistor, and the second end of the sampling resistor is grounded; the control electrode of the high-side switch tube is connected to the control electrode of the second transistor; the second electrode of the high-side switch tube is connected to a positive input end of the operational amplifier, the second electrode of the second transistor is connected to an inverting input end of the operational amplifier, and the output end of the operational amplifier is connected to the control electrode of the third transistor; the operational amplifier is used to work in a linear amplification state so that the second electrode of the high-side switch tube and the second electrode of the second transistor are in a virtual short state, so that the voltages on the second electrode of the high-side switch tube and the second electrode of the second transistor are the same, and the currents of the branch where the high-side switch tube is located and the branch where the second transistor is located are in a preset ratio. Among them, the input end of the voltage clamp circuit is connected to the second pole of the high-side switch tube, and the output end of the voltage clamp circuit is respectively connected to the control pole of the high-side switch tube and the control pole of the second transistor; the voltage clamp circuit is used to collect the first voltage on the second pole of the high-side switch tube, and output a voltage clamp signal when the first voltage is greater than the preset second voltage; the voltage clamp signal is used to clamp the voltage difference between the first pole and the second pole of the high-side switch tube to a preset third voltage. In this way, when the load current of the branch where the high-side switch tube is located is small, the offset voltage can be ignored compared with the third voltage, so as to reduce the influence of the offset voltage on the load current and ensure the sampling accuracy of the load current.

[0025] The beneficial effects provided in the above-mentioned other aspects and the possible designs of the above-mentioned other aspects can be referred to the beneficial effects brought about by the above-mentioned first aspect and the possible implementation methods of the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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.

[0027] Figure 1 A current sampling circuit for a high-side switch driving circuit provided in the related art;

[0028] Figure 2A schematic diagram of the structure of a current sampling circuit for a high-side switch driving circuit provided in an embodiment of the present application;

[0029] Figure 3 A schematic structural diagram of another current sampling circuit for a high-side switch driving circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] In the related art, when monitoring the current on the target transistor in the high-side switch driving circuit, a sampling transistor and an operational amplifier feedback loop are used to form a current sampling circuit, and the current of the branch where the sampling transistor is located is collected, so as to calculate the current value of the branch where the target transistor is located according to the size ratio of the target transistor and the sampling transistor, so as to realize the monitoring of the current value on the target transistor. However, since the operational amplifier feedback loop usually introduces an offset voltage, the current value of the branch where the sampling transistor is located and the current of the branch where the target transistor is located are not completely in the current mirror ratio, but there will be a certain error, so that the current sampling accuracy of the branch where the target transistor is located is low.

[0035] Figure 1 For related technologies, please refer to the current sampling circuit for high-side switch drive circuit. Figure 1 As shown, the high-side switch driving circuit includes a target transistor M1, and the current sampling circuit includes a sampling transistor M2, a transistor M3, a feedback operational amplifier EA1 and a power tube driving circuit 10. Among them, the target transistor M1 is a transistor in the high-side switch driving circuit, that is, a transistor to be controlled, so it is necessary to monitor the current on the target transistor M1. The first electrode of the target transistor M1 is connected to the switching power supply VS1, the second electrode of the target transistor M1 is connected to the first end of the first load Rload1, and the second end of the first load Rload1 is grounded GND; the first electrode of the sampling transistor M2 is also connected to the switching power supply VS, the second electrode of the sampling transistor M2 is connected to the first electrode of the transistor M3, the second electrode of the transistor M3 is connected to the first end of the first sampling resistor Rsns1, and the second end of the first sampling resistor Rsns1 is grounded GND. The control electrode of the target transistor M is connected to the control electrode of the sampling transistor M2. Among them, the driving end of the power tube driving circuit 10 is respectively connected to the control electrode of the target transistor M1 and the control electrode of the sampling transistor M2, and the power tube driving circuit 10 is used to output a driving signal to control the action of the target transistor M1 and the sampling transistor M2.

[0036] Among them, in order to realize the sampling of the current of the branch where the target transistor M1 is located, a sampling transistor and an operational amplifier feedback loop are used in the related technology to form a current sampling circuit, so as to facilitate the collection of the current value of the branch where the target transistor M1 and the first load Rload1 are located. Specifically, the second electrode of the target transistor M1 is connected to the non-inverting input terminal of the feedback operational amplifier EA1, the second electrode of the sampling transistor M2 is connected to the inverting input terminal of the feedback operational amplifier EA1, and the output terminal of the feedback operational amplifier EA1 is connected to the control electrode of the transistor M3; the feedback operational amplifier EA1 is used to work in a linear amplification state, so that the second electrode of the target transistor M1 and the second electrode of the sampling transistor M2 are in a virtual short state, so that the voltage of the second electrode of the target transistor M1 and the second electrode of the sampling transistor M2 are the same, that is, Figure 1 The voltages at VA1 and VB1 are the same.

[0037] Please continue to see Figure 1 As shown, assuming that the size ratio of the target transistor M1 and the sampling transistor M2 is K:1, during normal operation, the target transistor M1 and the sampling transistor M2 both work in the linear region, the on-resistance of the target transistor M1 is Rds1, and the on-resistance of the sampling transistor M2 is Rds2, then the impedance relationship between the target transistor M1 and the sampling transistor M2 is: K*Rds1=Rds2. In this embodiment, the loop control is realized by the feedback operational amplifier EA1, so that VA1=VB1, then the voltage drop across the target transistor M1 and the sampling transistor M2 is equal, assuming that the current value of the branch where the first load Rload1 is located is Iload1, and the sampling current value of the branch where the sampling resistor Rsns1 is located is Isns1, then Isns1=Iload1 / K, Isns1 current flows through the first sampling resistor Rsns1 and is converted into voltage information Vsns1, that is, Vsns1=Rsns1*Isns1.

[0038] Among them, since the feedback operational amplifier EA1 in the related art has an offset voltage Vos, VA1 = VB1 + Vos, that is, Ilaod1*Rds1+Vos=Isns1*Rds2=Vds1+Vos=Vds2, then Isns1=Iload1 / K+Vos / Rds2. When the load current Iload1 is large, the current value of Iload1 / K is also large, and Vos / Rds2 is a small current value. It can be seen that the offset voltage Vos has limited influence on the sampling accuracy; when the load current Iload1 is small, the current value of Iload1 / K is also small, and the error current value introduced by Vos / Rds2 will have a great influence on the sampling accuracy. In other words, the current sampling circuit driven by the high-side switch in the related art, due to the offset voltage Vos of the op amp, causes the sampling current Isns1 to be not equal to the ideal value Iload1 / K, and the error current Vos / Rds2 caused by Vos needs to be superimposed, that is, Isns1=Iload1 / K+Vos / Rds2. It can be seen from the formula that in the application scenario of small load current Iload1, the proportion of error current Vos / Rds2 becomes higher, resulting in a decrease in the accuracy of the sampled load current Iload1. It can be seen that due to the existence of the op amp offset voltage Vos, the existing current sampling scheme has a low sampling accuracy at small load currents and cannot meet application requirements.

[0039] In order to overcome the deficiencies in the above-mentioned related technologies, the present application provides a current sampling circuit for a high-side switch driving circuit. On the basis of the existing current sampling circuit, the current sampling circuit provided by the present application adds a voltage clamping circuit, the input end of the voltage clamping circuit is connected to the second pole of the high-side switch tube, and the output end of the voltage clamping circuit is respectively connected to the control pole of the high-side switch tube and the control pole of the second transistor. The voltage clamping circuit is used to collect the first voltage on the second pole of the high-side switch tube, and output a voltage clamping signal when the first voltage is greater than the preset second voltage; the voltage clamping signal is used to clamp the voltage difference between the first pole and the second pole of the high-side switch tube to a preset third voltage, that is, the voltage clamping circuit detects the voltage Vds1 of the high-side switch tube and adjusts it through a loop, and finally realizes that the voltage between the first pole and the second pole of the high-side switch tube is always not less than the third voltage Vclamp.

[0040] The voltage clamp circuit provided in the present application works only when the load current is less than a preset value, because when the load current is less than the preset value, the voltage Vds1 between the first and second electrodes of the high-side switch tube is less than the third voltage Vclamp. At this time, the voltage clamp circuit adjusts through the loop so that Vds1=Vds2=Vclamp. If the voltage clamp circuit is not added, the high-side switch tube and the second transistor always work in the linear region, and their on-resistance is very small. Under a small load current, the voltage difference between the first and second electrodes of the high-side switch tube and the second transistor is very small; when the voltage clamp circuit is added, when the load current Iload is small, the voltage difference between the second electrode and the control electrode of the high-side switch tube and the second transistor can be lowered, so that both the high-side switch tube and the second transistor work in the saturation region, and the on-resistance of the high-side switch tube and the second transistor becomes larger, so that the voltage Vds1 between the first and second electrodes of the high-side switch tube is equal to the designed third voltage Vclamp, and the voltage Vds2 between the first and second electrodes of the second transistor differs from Vds1 by an offset voltage Vos. At this time, Vds1 and Vds2 are larger voltage values ​​than the offset voltage Vos, and the offset voltage Vos is a smaller value. Therefore, the addition of the voltage clamp circuit provided by the present application makes it possible to ignore the Vos voltage in the formula Vds1+Vos=Vds2 when the load current Iload is small, thereby improving the current sampling accuracy at small load currents.

[0041] Figure 2 For a structural diagram of a current sampling circuit for a high-side switch driving circuit provided in an embodiment of the present application, see Figure 2 As shown, the high-side switch driving circuit provided in this embodiment includes a high-side switch tube Q1 , and the current sampling circuit includes: a second transistor Q2 , a third transistor Q3 , an operational amplifier EA, a sampling resistor Rsns and a voltage clamping circuit 20 .

[0042] Among them, the first electrode of the high-side switch tube Q1 is connected to the power supply VS, the second electrode of the high-side switch tube Q1 is connected to the first end of the load Rload, and the second end of the load Rload is grounded GND; the first electrode of the second transistor Q2 is also connected to the power supply VS, the second electrode of the second transistor Q2 is connected to the first electrode of the third transistor Q3, the second electrode of the third transistor Q3 is connected to the first end of the sampling resistor Rsns, and the second end of the sampling resistor Rsns is grounded; the control electrode of the high-side switch tube Q1 is connected to the control electrode of the second transistor Q2. The second electrode of the high-side switch tube Q1 is connected to the non-inverting input terminal of the operational amplifier EA, the second electrode of the second transistor Q2 is connected to the inverting input terminal of the operational amplifier EA, and the output terminal of the operational amplifier EA is connected to the control electrode of the third transistor Q3; the operational amplifier EA is used to work in a linear amplification state so that the second electrode of the high-side switch tube Q1 and the second electrode of the second transistor Q2 are in a virtual short state. At this time, Vds1+Vos=Vds2, Vds1 is the voltage difference between the first electrode and the second electrode of the high-side switch tube Q1, Vds2 is the voltage difference between the first electrode and the second electrode of the second transistor Q2, and Vos is the offset voltage of the operational amplifier EA.

[0043] The input end of the voltage clamp circuit 20 is connected to the second electrode of the high-side switch tube Q1, and the output end of the voltage clamp circuit 20 is respectively connected to the control electrode of the high-side switch tube Q1 and the control electrode of the second transistor Q2; the voltage clamp circuit 20 is used to collect the first voltage VOUT on the second electrode of the high-side switch tube Q1, and output the voltage clamp signal Igm when the first voltage VOUT is greater than the preset second voltage. The voltage clamp signal Igm is used to clamp the voltage difference Vds1 between the first electrode and the second electrode of the high-side switch tube Q1 to a preset third voltage Vclamp.

[0044] It can be seen that according to the current sampling circuit for the high-side switch driving circuit provided in this embodiment, when the load current Iload is small, the voltage difference between the second electrode and the control electrode of the high-side switch tube Q1 and the second transistor Q2 can be lowered, so that the high-side switch tube Q1 and the second transistor Q2 both work in the saturation region, and the on-resistance of the high-side switch tube Q1 and the second transistor Q2 becomes larger, so that the voltage Vds1 between the first electrode and the second electrode of the high-side switch tube Q1 is equal to the designed third voltage Vclamp, and the voltage Vds2 between the first electrode and the second electrode of the second transistor Q2 differs from Vds1 by an offset voltage Vos. At this time, Vds1 and Vds2 are larger voltage values ​​than the offset voltage Vos, and the offset voltage Vos is a smaller value. Therefore, the addition of the voltage clamping circuit provided in the present application makes the Vos voltage in the formula Vds1+Vos=Vds2 negligible when the load current Iload is small, thereby improving the current sampling accuracy at small load currents.

[0045] Specifically, in this embodiment, the above-mentioned high-side switch tube Q1 and the second transistor Q2 can both adopt NMOS (N-Metal-Oxide-Semiconductor) tubes, whose first pole is the drain, the second pole is the source, and the control pole is the gate; wherein the third transistor Q3 can adopt PMOS (N-Metal-Oxide-Semiconductor) tube, whose first pole is the source, the second pole is the drain, and the control pole is the gate.

[0046] Please continue to see Figure 2 As shown, the voltage clamp circuit 20 provided in this embodiment includes a transconductance operational amplifier GM and a transistor driving circuit 201. Among them, the positive phase input terminal of the transconductance operational amplifier GM is connected to the input terminal of the voltage clamp circuit 20, that is, the positive phase input terminal of the transconductance operational amplifier GM is connected to the second electrode of the high-side switch tube Q1, and is used to collect the first voltage VOUT on the second electrode of the high-side switch tube Q1; the inverting input terminal of the transconductance operational amplifier GM is used to receive the preset second voltage (VS-X); the transconductance operational amplifier GM is used to output the first current signal Igm when it is determined that the voltage difference between the first voltage VOUT and the second voltage (VS-X) is greater than zero. In other words, the transconductance operational amplifier GM is used to compare the first voltage VOUT and the second voltage (VS-X), and when the first voltage VOUT is greater than the second voltage (VS-X), the first current signal Igm is output. The transistor driving circuit 201 is used for generating a voltage clamping signal GATE under the triggering of the first current signal Igm, so as to clamp the voltage difference between the first electrode and the second electrode of the high-side switch tube Q1 to a preset third voltage Vclamp.

[0047] It can be understood that, since the control electrode of the high-side switch tube Q1 is connected to the control electrode of the second transistor Q2, the voltage clamping signal GATE generated by the transistor driving circuit 201 simultaneously clamps the voltage difference between the first electrode and the second electrode of the second transistor Q2 to a preset third voltage Vclamp. At this time, Vds1+Vos=Vds2.

[0048] For details, please refer to Figure 2 As shown, the output end of the transconductance operational amplifier GM of this embodiment is connected to the input end of the transistor driving circuit 201, and the input end of the transistor driving circuit 201 is used to receive the output first current signal Igm; the output end of the transistor driving circuit 201 is the output end of the voltage clamping circuit 20, and the output of the transistor driving circuit 201 is respectively connected to the control electrode of the high-side switch tube Q1 and the control electrode of the second transistor Q2.

[0049] In some embodiments, the voltage clamp signal GATE output by the transistor driving circuit 201 is substantially a second current signal; the second current signal is used to control the voltage difference between the control electrode and the second electrode of the high-side switch tube Q1 to be reduced to a fourth voltage. It can be understood that the second current signal will draw away the current injected into the load Rload, so that the current value flowing through the load Rload is reduced, thereby reducing the voltage difference between the second electrode and the control electrode of the high-side switch tube, so that both the high-side switch tube Q1 and the second transistor Q2 work in the saturation region, and the on-resistance of the high-side switch tube Q1 and the second transistor Q2 becomes larger, thereby increasing the voltage Vds1 between the first electrode and the second electrode of the high-side switch tube; correspondingly, the voltage difference Vds2 between the first electrode and the second electrode of the second transistor Q2 is also increased. At this time, Vds1 and Vds2 are larger voltage values ​​than the offset voltage Vos, and the offset voltage Vos is a smaller value. Therefore, the addition of the voltage clamp circuit provided in the present application enables the offset voltage Vos to be negligible in the formula Vds1+Vos=Vds2 when the load current Iload is small, thereby improving the current sampling accuracy at small load currents.

[0050] Please continue to see Figure 2 As shown, in this embodiment, the first electrode of the high-side switch tube Q1 can be specifically a drain electrode, the second electrode of the high-side switch tube Q1 can be a source electrode, and the control electrode of the high-side switch tube Q1 can be a gate electrode. Correspondingly, the first electrode of the second transistor Q2 can be specifically a drain electrode, the second electrode of the second transistor Q2 can be a source electrode, and the control electrode of the second transistor Q2 can be a gate electrode. The first electrode of the third transistor Q3 can be specifically a source electrode, the second electrode of the third transistor Q3 can be a drain electrode, and the control electrode of the third transistor Q3 can be a gate electrode. Among them, for the high-side switch tube Q1, the voltage difference between its second electrode and the control electrode is the voltage difference between the source electrode and the gate electrode, and the voltage difference between the source electrode and the gate electrode can be expressed as Vgs1, and the voltage difference between its first electrode and the second electrode is the voltage difference between the drain electrode and the source electrode, and the voltage difference between the drain electrode and the source electrode can be expressed as Vds1. For the second transistor Q2, the voltage difference between its second electrode and the control electrode is the voltage difference between the source and the gate, and the voltage difference between the source and the gate can be expressed as Vgs2. The voltage difference between its first electrode and the second electrode is the voltage difference between the drain and the source, and the voltage difference between the drain and the source can be expressed as Vds2.

[0051] Please continue to see Figure 2As shown, it can be seen that the equivalent transconductance of the transconductance operational amplifier GM of this embodiment is a fixed value gm, the non-inverting input terminal of the transconductance operational amplifier GM is input as the first voltage VOUT, the inverting input terminal of the transconductance operational amplifier GM is input as the second voltage (VS-X), the second voltage (VS-X) is a preset fixed value, X is a fixed voltage value, and the transconductance operational amplifier GM outputs the first current signal Igm. If △Vin=VOUT-VS+X is greater than 0V, the first current signal Igm is output. Among them, Igm=gm*□Vin, the larger the △Vin is, the larger the current value of the output first current signal Igm is. It can be understood that when the first voltage VOUT is high, if the △Vin value is large, the value of the load current Iload in the sampling circuit is small at this moment.

[0052] Among them, for the transistor driving circuit 201, if the first current signal Igm output by the transconductance operational amplifier GM is received, the transistor driving circuit 201 controls the voltage Vgs1 of the high-side switch tube Q1 and the voltage Vgs2 of the second transistor Q2 to decrease, so that the on-impedance of the high-side switch tube Q and the second transistor Q2 becomes larger. When the load current Iload is constant, the first voltage VOUT becomes smaller, that is, the voltage Vds1 of the high-side switch tube Q1 and the voltage Vds2 of the second transistor Q2 become larger, so that the offset voltage Vos can be ignored, thereby improving the current sampling accuracy at small load currents.

[0053] It can be understood that, in other embodiments, if the current value of the first current signal Igm output by the transconductance operational amplifier GM increases, the transistor driving circuit 201 controls the Vgs1 of the high-side switch tube Q1 and the Vgs2 of the second transistor Q2 to decrease, so that the on-resistance of the high-side switch tube Q1 and the second transistor Q2 increases. When the load current Iload is constant, the first voltage VOUT decreases, that is, the voltage Vds1 of the high-side switch tube Q1 and the Vds2 of the second transistor Q2 increase. If the current value of the first current signal Igm output by the transconductance operational amplifier GM decreases, the transistor driving circuit 201 controls the Vgs1 of the high-side switch tube Q1 and the Vgs2 of the second transistor Q2 to increase, so that the on-resistance of the high-side switch tube Q1 and the second transistor Q2 decreases; accordingly, the first voltage VOUT increases, that is, the voltage Vds1 of the high-side switch tube Q1 and the Vds2 of the second transistor Q2 decreases.

[0054] It can be seen that in this embodiment, the voltage difference Vds1 between the drain and source of the high-side switch Q1 is clamped to the third voltage Vclamp by relying on the loop regulation of the voltage clamp circuit 20; △Vin=VOUT-VS+X is a fixed quantity, that is, the first voltage VOUT is a stable voltage, and the magnitude of the first voltage VOUT is determined by X, which can be set by technicians according to the actual circuit application scenario. In other words, in the current sampling circuit provided in this embodiment, due to the design of the voltage clamp circuit 20, when the load current Iload is small, the offset voltage Vos in the formula Vds1+Vos=Vds2 can be ignored, thereby improving the sampling accuracy of small currents, and the value of the third voltage Vclamp can be adjusted by adjusting the value of X.

[0055] It is understandable that when the load current Iload is large, the first voltage VOUT is small, and the high-side switch tube Q1 already satisfies Vds1>Vclanp. At this time, the operational amplifier offset voltage Vos in the high-side sampling circuit has a very limited effect on the sampling accuracy, and the voltage clamping circuit 20 does not work at this time. In this scenario, △Vin=VOUT-VS+X, △Vin does not reach the preset value or is less than 0, that is, the transconductance operational amplifier GM does not generate the first current signal Igm at this time, or the generated first current signal Igm does not reach the preset value, and the transistor driving circuit 201 cannot be triggered to pull down Vgs1 of the high-side switch tube Q1 and Vgs2 of the second transistor Q2. At this time, the high-side switch tube Q1 and the second transistor Q2 are still working in the linear region, and the on-resistance of the high-side switch tube Q1 and the second transistor Q2 is very small, but because the load current Iload is large enough, Vds1>Vclamp is satisfied, and the sampling accuracy can meet the application requirements.

[0056] Please continue to see Figure 2 As shown, the first end of the sampling resistor Rsns is a voltage sampling end, and the voltage sampling end is used to collect the sampling voltage value Vsns on the first end of the sampling resistor Rsns. Then, the sampling current value Isns can be calculated according to the sampling voltage value Vsns and the resistance value of the sampling resistor Rsns. Then, the load current Iload can be calculated according to the size ratio K of the high-side switch tube Q1 and the second transistor Q2 and the offset voltage Vo.

[0057] Figure 3 For a structural diagram of another current sampling circuit for a high-side switch driving circuit provided in an embodiment of the present application, see Figure 3As shown, in some embodiments, the current sampling circuit for the high-side switch driving circuit further includes a sampling current calculation circuit 30. The input end of the sampling current calculation circuit 30 is connected to the voltage sampling end, and is used to obtain the sampling voltage value Vsns. The sampling current calculation circuit 30 is used to calculate the load current value Iload of the loop where the load is located according to the sampling voltage value Vsns, the resistance value of the sampling resistor Rsns, the size ratio K of the high-side switch tube Q1 and the second transistor Q2, the on-resistance Rds2 of the second transistor Q2, and the offset voltage Vos of the operational amplifier.

[0058] Specifically, in this embodiment, the load current value Iload of the load loop is calculated based on the sampled voltage value Vsns, the resistance value of the sampling resistor Rsns, the size ratio K of the high-side switch Q1 and the second transistor Q2, the on-resistance Rds2 of the second transistor Q2, and the offset voltage Vos of the operational amplifier, including:

[0059] Calculate the load current value Iload of the load circuit according to the following formula (1):

[0060] Iload=K*(Isns-Vos / Rds2) (1)

[0061] In the above formula (1), Iload is the load current value, K is the size ratio of the high-side switch tube Q1 and the second transistor Q2, Isns is the current value calculated according to the sampling voltage value Vsns and the resistance value of the sampling resistor Rsns, and Rds2 is the on-resistance of the second transistor.

[0062] Based on the current sampling circuit for the high-side switch driving circuit provided in the above embodiments, this embodiment further provides a high-side switch driving circuit, which includes the current sampling circuit as described above. It can be seen from the above description that the high-side switch driving circuit provided in this embodiment can accurately collect the current value of the branch where the target transistor and the load are located, so as to realize accurate monitoring of the load current.

[0063] On the basis of the current sampling circuit for the high-side switch driving circuit provided in the above embodiments, this embodiment further provides a chip, and the chip includes the above current sampling circuit.

[0064] Based on the current sampling circuit for the high-side switch driving circuit provided in the above embodiments, this embodiment further provides an electronic device, which includes the above current sampling circuit; or the electronic device includes the above chip.

[0065] 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 a high-side switch driving circuit, the high-side switch driving circuit comprising a high-side switch tube, a first electrode of the high-side switch tube being connected to a power supply, a second electrode of the high-side switch tube being connected to a first end of a load, and a second end of the load being grounded; characterized in that: The current sampling circuit comprises: a second transistor, a third transistor, an operational amplifier, a sampling resistor and a voltage clamping circuit; The first electrode of the second transistor is also connected to the power supply, the second electrode of the second transistor is connected to the first electrode of the third transistor, the second electrode of the third transistor is connected to the first end of the sampling resistor, and the second end of the sampling resistor is grounded; the control electrode of the high-side switch is connected to the control electrode of the second transistor; The second electrode of the high-side switch is connected to the non-inverting input terminal of the operational amplifier, the second electrode of the second transistor is connected to the inverting input terminal of the operational amplifier, and the output terminal of the operational amplifier is connected to the control electrode of the third transistor; the operational amplifier is used to work in a linear amplification state so that the second electrode of the high-side switch and the second electrode of the second transistor are in a virtual short state; The input end of the voltage clamping circuit is connected to the second pole of the high-side switch tube, and the output end of the voltage clamping circuit is respectively connected to the control pole of the high-side switch tube and the control pole of the second transistor; the voltage clamping circuit is used to collect the first voltage on the second pole of the high-side switch tube, and output a voltage clamping signal when the first voltage is greater than a preset second voltage; the voltage clamping signal is used to clamp the voltage difference between the first pole and the second pole of the high-side switch tube to a preset third voltage.

2. The current sampling circuit for a high-side switch driving circuit according to claim 1, characterized in that: The voltage clamping circuit includes a transconductance operational amplifier and a transistor driving circuit; The non-inverting input terminal of the transconductance operational amplifier is connected as the input terminal of the voltage clamp circuit, and is used to collect the first voltage on the second electrode of the high-side switch tube; The inverting input terminal of the transconductance operational amplifier is used to receive the preset second voltage; the transconductance operational amplifier is used to output a first current signal when it is determined that the voltage difference between the first voltage and the second voltage is greater than zero; The transistor driving circuit is used to generate the voltage clamping signal under the triggering of the first current signal, so as to clamp the voltage difference between the first electrode and the second electrode of the high-side switch tube to a preset third voltage.

3. The current sampling circuit for a high-side switch driving circuit according to claim 1 or 2, characterized in that: The output end of the transconductance operational amplifier is connected to the input end of the transistor driving circuit, and the input end of the transistor driving circuit is used to receive the output first current signal; the output end of the transistor driving circuit is the output end of the voltage clamping circuit, and the output of the transistor driving circuit is respectively connected to the control electrode of the high-side switch tube and the control electrode of the second transistor.

4. The current sampling circuit for a high-side switch driving circuit according to any one of claims 1 to 3, characterized in that: The voltage clamping signal is a second current signal; the second current signal is used to control the voltage difference between the control electrode and the second electrode of the high-side switch tube to be reduced to a fourth voltage.

5. The current sampling circuit for a high-side switch driving circuit according to claim 1 or 2, characterized in that: The first end of the sampling resistor is a voltage sampling end, and the voltage sampling end is used to sample a sampling voltage value on the first end of the sampling resistor.

6. The current sampling circuit for a high-side switch driving circuit according to claim 5, characterized in that: Also includes a sampling current calculation circuit; The input end of the sampling current calculation circuit is connected to the voltage sampling end to obtain the sampling voltage value; The sampling current calculation circuit is used to calculate the load current value of the loop where the load is located based on the sampling voltage value, the resistance value of the sampling resistor, the size ratio of the high-side switch tube and the second transistor, the on-resistance of the second transistor and the offset voltage of the operational amplifier.

7. The current sampling circuit for a high-side switch driving circuit according to claim 6, characterized in that: The load current value of the loop where the load is located is calculated according to the sampled voltage value, the resistance value of the sampling resistor, the size ratio of the high-side switch tube and the second transistor, the on-resistance of the second transistor, and the offset voltage of the operational amplifier, and includes: The load current value of the circuit where the load is located is calculated according to the following formula (1): Iload=K*(Isns-Vos / Rds2) (1) In the above formula (1), Iload is the load current value, K is the size ratio of the high-side switch tube and the second transistor, Isns is the current value calculated based on the sampled voltage value and the sampling resistor, and Rds2 is the on-resistance of the second transistor.

8. A high side switch driving circuit, characterized in that: The invention comprises a current sampling circuit as described in any one of claims 1 to 7.

9. A chip, characterized in that: The invention comprises a current sampling circuit as described in any one of claims 1 to 7.

10. An electronic device, characterized in that: Includes the current sampling circuit as described in any one of claims 1 to 7; or includes the chip as described in claim 9.

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