A current detection circuit and a current shunt

Abstract

The present invention discloses a current detection circuit and a shunt, wherein the current detection circuit includes a shunt resistor, a fully differential amplifier, a reference voltage output module and a subtractor, wherein the fully differential amplifier performs a first-stage amplification on the voltage across the shunt resistor to obtain a first output voltage, the reference voltage output module is used to provide a reference voltage for the subtractor, and the subtractor performs a second-stage amplification based on the first output voltage and the reference voltage to obtain a second output voltage, and the second output voltage is less than or equal to the first power supply voltage. It can be seen that the present application provides a reference voltage with a value equal to half of the first power supply voltage to the subtractor through the reference voltage output module, so that the absolute value of the voltage across the shunt resistor after two amplifications is less than or equal to half of the first power supply voltage, thereby realizing the measurement of bidirectional current and increasing the application scenarios of current detection.

Description

Technical Field

[0001] The present invention relates to the technical field of current detection, and in particular to a current detection circuit and a shunt. Background Art

[0002] Current detection is widely used in electronic systems. It can not only be used for overcurrent protection, but also for external torque control of motors and commutation operations using external controllers to ensure that electronic systems can operate safely, stably and efficiently. At present, the current detection method is mainly based on shunts for current detection. Existing shunts are usually composed of two resistors in parallel, one of which is called a shunt resistor, which is used to measure current; the other resistor is called a bypass resistor, which is used to provide a low-impedance path to prevent the shunt resistor from overheating and being damaged. The output voltage of the shunt can reflect the current flowing through the shunt resistor, and the current is detected by detecting the current flowing through the shunt resistor. Currently existing shunts can usually only measure unidirectional current, which is limited for application scenarios that require measuring bidirectional current. Summary of the invention

[0003] The purpose of the present invention is to provide a current detection circuit and a shunt, so that the absolute value of the voltage across the shunt resistor after two amplifications is less than or equal to half of the first power supply voltage, thereby realizing the measurement of bidirectional current and increasing the application scenarios of current detection.

[0004] In order to solve the above technical problems, the present invention provides a current detection circuit, comprising:

[0005] A shunt resistor, wherein the shunt resistor is arranged in the circuit to be tested;

[0006] A fully differential amplifier, wherein the input end of the fully differential amplifier is connected to the two ends of the shunt resistor, and the output end is connected to the input end of the subtractor, and is used to perform a first-stage amplification on the voltage across the two ends of the shunt resistor to obtain a first output voltage;

[0007] A reference voltage output module, the output end of which is connected to the reference end of the subtractor, and is used to provide a reference voltage for the subtractor, wherein the reference voltage is half of the first power supply voltage of the subtractor;

[0008] The subtractor is used to perform secondary amplification on the first output voltage, and obtain a second output voltage based on the voltage after the secondary amplification and the reference voltage, and the second output voltage is less than or equal to the first power supply voltage.

[0009] Optionally, the input stage module of the fully differential amplifier includes:

[0010] Current limiting resistor;

[0011] A first PMOS transistor, wherein a gate of the first PMOS transistor is connected to a control signal, a source of the first PMOS transistor is connected to a second power supply voltage of the fully differential amplifier, and a drain of the first PMOS transistor is connected to a first end of the current limiting resistor;

[0012] a second PMOS transistor, wherein the gate of the second PMOS transistor is connected to the first end of the shunt resistor, the source is connected to the second end of the current limiting resistor, and the drain is connected to the first input end of the output stage module of the fully differential amplifier;

[0013] a third PMOS tube, wherein the gate of the third PMOS tube is connected to the second end of the shunt resistor, the source of the third PMOS tube is connected to the second end of the current limiting resistor, and the drain of the third PMOS tube is connected to the second input end of the output stage module of the fully differential amplifier;

[0014] The first PMOS tube, the second PMOS tube and the third PMOS tube are all PMOS tubes whose withstand voltage values ​​are greater than a preset voltage value.

[0015] Optionally, the input stage module of the fully differential amplifier further includes:

[0016] A fourth PMOS tube, wherein the gate and drain of the fourth PMOS tube are both connected to the second power supply voltage, the source is connected to the gate of the first PMOS tube, and the fourth PMOS tube is an isolated PMOS tube.

[0017] Optionally, the input stage module of the fully differential amplifier further includes:

[0018] a first diode, wherein an anode of the first diode is connected to a gate of the second PMOS tube, and a cathode of the first diode is connected to a first end of the current limiting resistor;

[0019] A second diode, wherein an anode of the second diode is connected to the gate of the third PMOS tube, and a cathode of the second diode is connected to the first end of the current limiting resistor.

[0020] Optionally, also include:

[0021] A first switch control module, wherein the output end of the first switch control module is connected to the gate of the first PMOS tube, and is used to output the control signal to control whether the fully differential amplifier works.

[0022] Optionally, the reference voltage output module includes:

[0023] A first reference voltage-dividing resistor, a first end of which is connected to the first power supply voltage;

[0024] a second reference voltage-dividing resistor, wherein a first end of the second reference voltage-dividing resistor is grounded, and a second end of the second reference voltage-dividing resistor is respectively connected to the second end of the first reference voltage-dividing resistor and the input end of the voltage follower, and the first reference voltage-dividing resistor and the second reference voltage-dividing resistor are equal in size;

[0025] A voltage follower, wherein the output terminal of the voltage follower is connected to the reference terminal of the subtractor.

[0026] Optionally, the subtractor includes a differential amplifier, a first input resistor, a second input resistor, a first feedback resistor and a second feedback resistor, wherein the first end of the first input resistor is connected to the positive output end of the fully differential amplifier, and the second end is respectively connected to the negative phase input end of the differential amplifier and the first end of the first feedback resistor, the second end of the first feedback resistor is connected to the output end of the differential amplifier, the first end of the second input resistor is connected to the negative output end of the fully differential amplifier, and the second end is respectively connected to the positive phase input end of the differential amplifier and the first end of the second feedback resistor, the second end of the second feedback resistor is connected to the output end of the reference voltage output module, the power supply end of the differential amplifier is connected to the first power supply voltage, the first input resistor and the second input resistor have the same resistance value, and the first feedback resistor and the second feedback resistor have the same resistance value;

[0027] The first feedback resistor and the second feedback resistor are adjustable resistors.

[0028] Optionally, the first feedback resistor and the second feedback resistor both include:

[0029] A first feedback voltage-dividing resistor, a second feedback voltage-dividing resistor, and finally an Nth feedback voltage-dividing resistor;

[0030] A first switch, a second switch, and so on to an Nth switch, where N is an integer not less than 2;

[0031] The first end of the first switch, the first end of the second switch and the first end of the Nth switch are connected, and a common end of the connections serves as a first end of a corresponding feedback resistor;

[0032] The second end of the i-th switch is connected to the first end of the i-th feedback voltage-dividing resistor, the second end of the i-th feedback voltage-dividing resistor is connected to the first end of the (i+1)-th feedback voltage-dividing resistor, the second end of the N-th feedback voltage-dividing resistor serves as the second end of the corresponding feedback resistor, and i is a positive integer less than N.

[0033] Optionally, also include:

[0034] The second switch control module is connected to the control ends of the first switch, the second switch, and the Nth switch respectively, and is used to control the on or off of the first switch, the second switch, and the Nth switch.

[0035] In order to solve the above technical problem, the present invention further provides a shunt, comprising a bypass resistor and the above current detection circuit, wherein two ends of the bypass resistor are connected in parallel with the shunt resistor in the current detection circuit.

[0036] The present application provides a current detection circuit and a shunt, wherein the current detection circuit includes a shunt resistor, a fully differential amplifier, a reference voltage output module, and a subtractor, wherein the fully differential amplifier performs a first-stage amplification on the voltage across the shunt resistor to obtain a first output voltage, the reference voltage output module is used to provide a reference voltage for the subtractor, and the subtractor performs a second-stage amplification based on the first output voltage and the reference voltage to obtain a second output voltage, and the second output voltage is less than or equal to the first power supply voltage. It can be seen that the present application provides a reference voltage equal to half of the first power supply voltage to the subtractor through the reference voltage output module, so that the absolute value of the voltage across the shunt resistor after two amplifications is less than or equal to half of the first power supply voltage, thereby realizing the measurement of bidirectional current and increasing the application scenarios of current detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 A schematic diagram of a current detection circuit provided by the present invention;

[0039] Figure 2 A schematic diagram of a half-bridge circuit provided by the present invention;

[0040] Figure 3 A schematic diagram of the structure of a fully differential amplifier provided by the present invention;

[0041] Figure 4 A schematic structural diagram of an input stage module of a fully differential amplifier provided by the present invention;

[0042] Figure 5 A schematic diagram of the structure of a reference voltage output module provided by the present invention;

[0043] Figure 6 A schematic diagram of the structure of a subtractor provided by the present invention;

[0044] Figure 7 A schematic diagram of the structure of an adjustable resistor provided by the present invention. DETAILED DESCRIPTION

[0045] The core of the present invention is to provide a current detection circuit and a shunt, so that the absolute value of the voltage across the shunt resistor after two amplifications is less than or equal to half of the first power supply voltage, thereby realizing the measurement of bidirectional current and increasing the application scenarios of current detection.

[0046] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] At present, the current detection method is mainly based on shunts for current detection. Existing shunts are usually composed of two parallel resistors, one of which is called a shunt resistor, which is used to measure current; the other resistor is called a bypass resistor, which is used to provide a low impedance path to prevent the shunt resistor from overheating and being damaged. The output voltage of the shunt can reflect the current flowing through the shunt resistor, and the current is detected by detecting the current flowing through the shunt resistor. Currently, existing shunts can usually only measure unidirectional current, which is limited for application scenarios that require measuring bidirectional current.

[0048] In order to solve the above technical problem, the present invention provides a current detection circuit.

[0049] Specifically, see Figure 1 As shown, Figure 1 A schematic diagram of a current detection circuit provided by the present invention.

[0050] The current detection circuit comprises:

[0051] Shunt resistor 1, shunt resistor 1 is set in the circuit to be tested;

[0052] A fully differential amplifier 2, wherein the input end of the fully differential amplifier 2 is connected to the two ends of the shunt resistor 1, and the output end is connected to the input end of the subtractor 4, and is used to perform a first-stage amplification on the voltage across the two ends of the shunt resistor 1 to obtain a first output voltage;

[0053] A reference voltage output module 3, the output end of which is connected to the reference end of the subtractor 4, for providing a reference voltage for the subtractor 4, wherein the reference voltage is half of the first power supply voltage of the subtractor 4;

[0054] The subtractor 4 is used to perform secondary amplification on the first output voltage, and obtain a second output voltage based on the secondary amplified voltage and a reference voltage, wherein the second output voltage is less than or equal to the first power supply voltage.

[0055] The current detection circuit includes a shunt resistor 1, a fully differential amplifier 2, a reference voltage output module 3 and a subtractor 4. The fully differential amplifier 2 of the present invention adopts a fully differential structure, and the current detection circuit adopts a symmetrical structure, which is less affected by the external environment and has a strong anti-interference ability. Wherein, the subtractor 4 includes a differential amplifier, a first input resistor, a second input resistor, a first feedback resistor and a second feedback resistor. The first end of the first input resistor is connected to the positive output end of the fully differential amplifier 2, and the second end is respectively connected to the negative phase input end of the differential amplifier and the first end of the first feedback resistor. The second end of the first feedback resistor is connected to the output end of the differential amplifier, the first end of the second input resistor is connected to the negative output end of the fully differential amplifier 2, and the second end is respectively connected to the positive phase input end of the differential amplifier and the first end of the second feedback resistor. The second end of the second feedback resistor is connected to the output end of the reference voltage output module 3, the power supply end of the differential amplifier is connected to the first power supply voltage, the first input resistor and the second input resistor have the same resistance value, and the first feedback resistor and the second feedback resistor have the same resistance value.

[0056] In this embodiment, the function of the shunt resistor 1 is to convert the current signal in the circuit into a voltage signal for easy measurement. The function of the fully differential amplifier 2 is to amplify the voltage across the shunt resistor 1 in one stage, and only amplify the differential signal in one stage to obtain the first output voltage, which improves the accuracy of current detection and suppresses common-mode noise, thereby ensuring the accuracy and stability of the voltage signal. In addition, the fully differential amplifier 2 can also amplify the tiny voltage signal to a measurable range. Then the reference voltage output module 3 changes the first power supply voltage of the subtractor 4 to half of the first power supply voltage to provide the subtractor 4 with a reference voltage of half of the first power supply voltage. The subtractor 4 performs a second-stage amplification on the first output voltage. The voltage after the second-stage amplification is the product of the gain of the differential amplifier and the first output voltage, and the sum of the voltage after the second-stage amplification and the reference voltage is used as the second output voltage. Since the differential amplifier of the subtractor 4 is a rail-to-rail output operational amplifier, the output level range of the subtractor 4 is 0 to the first power supply voltage, so the second output voltage is less than or equal to the first power supply voltage, then the second output voltage is:

[0057] (1);

[0058] Among them, the gain of the fully differential amplifier is G1, the gain of the differential amplifier is G2, the product of the gain of the fully differential amplifier G1 and the gain of the differential amplifier G2 is G, and the voltage across the shunt resistor is ( ), V REF / 2 is the reference voltage, and the second output voltage is V SO , the first output voltage is .

[0059] Since the differential amplifier of the subtractor is a rail-to-rail output operational amplifier, the voltage range of the second output voltage is from 0 to the first power supply voltage, so the second output voltage is:

[0060] (2);

[0061] Among them, V REF is the first power supply voltage, V REF / 2 is the reference voltage, the product of the gain of the fully differential amplifier and the gain of the differential amplifier is G, and the voltage across the shunt resistor is ( ); so the absolute value of the voltage after the secondary amplification is less than or equal to half of the first power supply voltage, and the voltage across the shunt resistor 1 can be positive or negative, that is, the direction of the current can be bidirectional. Among them, the first power supply voltage of the subtractor 4 can be a 3.3V logic level.

[0062] In practical applications, the current in the circuit of the driver driving the motor can be detected. The circuit of the driving motor can adopt a half-bridge circuit, which includes two power MOS tubes. The shunt resistor 1 can be set on the half-bridge circuit. One end of the shunt resistor 1 connected to the half-bridge circuit is SP, and the other end is SN. Correspondingly, the potential corresponding to the SP end is V SP , the potential corresponding to one end of SN is V SN For details, please see Figure 2 As shown, Figure 2 A schematic diagram of a half-bridge circuit provided by the present invention.

[0063] It can be seen that the present application provides a reference voltage equal to half of the first power supply voltage to the subtractor 4 through the reference voltage output module 3, so that the absolute value of the voltage across the shunt resistor 1 after two amplifications is less than or equal to half of the first power supply voltage, thereby realizing the measurement of bidirectional current and increasing the application scenarios of current detection.

[0064] Based on the above embodiments:

[0065] As an optional embodiment, the input stage module of the fully differential amplifier 2 includes:

[0066] Current limiting resistor;

[0067] A first PMOS transistor, wherein a gate of the first PMOS transistor is connected to a control signal, a source of the first PMOS transistor is connected to a second power supply voltage of the fully differential amplifier 2, and a drain of the first PMOS transistor is connected to a first end of a current limiting resistor;

[0068] A second PMOS tube, wherein the gate of the second PMOS tube is connected to the first end of the shunt resistor 1, the source is connected to the second end of the current limiting resistor, and the drain is connected to the first input end of the output stage module of the fully differential amplifier 2;

[0069] A third PMOS tube, wherein the gate of the third PMOS tube is connected to the second end of the shunt resistor 1, the source is connected to the second end of the current limiting resistor, and the drain is connected to the second input end of the output stage module of the fully differential amplifier 2;

[0070] The first PMOS tube, the second PMOS tube and the third PMOS tube are all PMOS tubes whose withstand voltage values ​​are greater than a preset voltage value.

[0071] For details, please refer to Figure 3 As shown, Figure 3 The schematic diagram of the structure of a fully differential amplifier provided by the present invention is shown in FIG. 1 , wherein the first output voltage of the fully differential amplifier 2 is the product of the gain of the fully differential amplifier 2 and the voltage drop across the shunt resistor 1, the gain of the fully differential amplifier 2 is the ratio of the feedback resistor of the fully differential amplifier 2 to the input resistor of the fully differential amplifier 2, the voltage range of the second power supply voltage can be 12.4V~47.5V, and the first output voltage of the fully differential amplifier 2 is:

[0072] (3);

[0073] Among them, the first output voltage is , the gain of the fully differential amplifier is G1, and the voltage across the shunt resistor is ( ).

[0074] For example, if the input resistance of the fully differential amplifier is 200 kΩ, and the feedback resistance of the fully differential amplifier is 400 kΩ, then the gain of the fully differential amplifier 2 is:

[0075] (4);

[0076] Among them, the gain of the fully differential amplifier is G1.

[0077] Compared with NMOS tubes, PMOS tubes have lower noise coefficients, which helps reduce noise interference in the input stage module of the fully differential amplifier 2, thereby improving the noise performance of the entire fully differential amplifier 2. In addition, in order to improve measurement accuracy and ensure normal operation under high and low voltage conditions, thereby meeting the needs of different application scenarios, this embodiment uses PMOS tubes with a withstand voltage greater than a preset voltage value as differential input pairs of tubes for the input stage module of the fully differential amplifier 2. PMOS tubes with a withstand voltage greater than the preset voltage value can operate at a higher power supply voltage, thereby improving the accuracy of current detection. Please refer to Figure 4 As shown, Figure 4 A schematic structural diagram of an input stage module of a fully differential amplifier provided by the present invention.

[0078] It should be noted that, in order to provide a stable DC operating point for the input stage module of the fully differential amplifier 2 so that each PMOS tube can work normally in the saturation region, a bias current is set between the second power supply voltage and the first PMOS tube to ensure the stability of the fully differential amplifier 2. In practical applications, when the control signal is at a high level, the current detection circuit does not work; when the control signal is at a low level, the current detection circuit works.

[0079] It can be seen that this embodiment uses a PMOS tube with a withstand voltage greater than a preset voltage value as a differential input pair tube of the input stage module of the fully differential amplifier 2, so that the current detection circuit can operate at a higher power supply voltage, thereby improving the accuracy of current detection.

[0080] As an optional embodiment, the input stage module of the fully differential amplifier 2 further includes:

[0081] A fourth PMOS tube, a gate and a drain of the fourth PMOS tube are both connected to the second power supply voltage, a source is connected to the gate of the first PMOS tube, and the fourth PMOS tube is an isolated PMOS tube.

[0082] In order to protect the first MOS tube, in this embodiment, an isolated PMOS tube is used to connect between the gate and source of the first MOS tube, so as to realize the isolation function of the circuit and prevent the current of the previous electrode from leaking into the subsequent circuit, thereby ensuring the normal operation of the current detection circuit. Specifically, since the isolated PMOS tube has an isolation function, the reverse breakdown characteristics of the isolated PMOS tube can be effectively utilized. When the input voltage exceeds the breakdown voltage of the isolated PMOS tube, the isolated PMOS tube will enter a reverse breakdown state, thereby limiting the voltage between the gate and the source of the first PMOS tube, and avoiding the first PMOS tube from being broken down. In addition, when the isolated PMOS is used as an isolation device, compared with a diode, it will hardly generate a voltage drop when it is turned on, so it can better protect the circuit and improve the overall performance and reliability of the fully differential amplifier 2.

[0083] It can be seen that this embodiment uses an isolated PMOS tube connected between the gate and source of the first PMOS tube, which can effectively utilize the reverse breakdown characteristics of the isolated PMOS tube. When the input voltage exceeds the breakdown voltage of the isolated PMOS tube, the isolated PMOS tube will enter a reverse breakdown state, thereby limiting the voltage between the gate and the source of the first PMOS tube to avoid its breakdown, thereby effectively protecting the first PMOS tube.

[0084] As an optional embodiment, the input stage module of the fully differential amplifier 2 further includes:

[0085] A first diode, wherein an anode of the first diode is connected to a gate of the second PMOS tube, and a cathode of the first diode is connected to a first end of a current limiting resistor;

[0086] A second diode, wherein an anode of the second diode is connected to the gate of the third PMOS tube, and a cathode of the second diode is connected to the first end of the current limiting resistor.

[0087] In order to protect the second PMOS tube and the third PMOS tube, in this embodiment, diodes are respectively arranged between the gate and the source of the second PMOS tube and the third PMOS tube. The diodes have a higher reverse breakdown voltage and can provide protection under overvoltage conditions. When the voltage between the gate and the source of the PMOS tube exceeds the reverse breakdown voltage of the diode, the diode will enter a reverse breakdown state, thereby limiting the voltage between the gate and the source of the first PMOS tube and preventing the PMOS tube from being broken down.

[0088] It can be seen that the present embodiment uses diodes connected between the gate and source of the second PMOS tube and the third PMOS tube, respectively, and can effectively utilize the reverse breakdown characteristics of the diode. When the input voltage exceeds the breakdown voltage of the diode, the diode will enter a reverse breakdown state, thereby limiting the voltage between the gate and the source of the PMOS tube to prevent it from being broken down, thereby effectively protecting the PMOS tube.

[0089] As an optional embodiment, it also includes:

[0090] The first switch control module has an output end connected to the gate of the first PMOS tube and is used to output a control signal to control whether the fully differential amplifier 2 works.

[0091] In this embodiment, the switch control module can receive feedback signals from the fully differential amplifier 2, such as differential feedback signals, and generate corresponding control signals based on these signals. These control signals can be pulse width modulation signals. When the control signal is at a high level, the current detection circuit does not work; when the control signal is at a low level, the current detection circuit works.

[0092] It can be seen that this embodiment uses the second switch control module to control the size of the control signal to control the operation of the current detection circuit.

[0093] As an optional embodiment, the reference voltage output module 3 includes:

[0094] A first reference voltage-dividing resistor, a first end of which is connected to a first power supply voltage;

[0095] A second reference voltage-dividing resistor, wherein a first end of the second reference voltage-dividing resistor is grounded, and a second end of the second reference voltage-dividing resistor is respectively connected to a second end of the first reference voltage-dividing resistor and an input end of the voltage follower, and the first reference voltage-dividing resistor and the second reference voltage-dividing resistor are equal in size;

[0096] A voltage follower, the output end of the voltage follower is connected to the reference end of the subtractor 4.

[0097] In order to provide a reference voltage to the subtractor 4, so that the second output voltage obtained by the voltage after secondary amplification and the reference voltage is less than or equal to the first power supply voltage, so that the absolute value of the voltage after secondary amplification is less than or equal to half of the first power supply voltage, the present embodiment sets a first reference voltage-dividing resistor and a second reference voltage-dividing resistor in one-to-one correspondence between the input end of the voltage follower and the first power supply voltage and the ground, so that the output end of the voltage follower outputs half of the first power supply voltage. For details, please refer to Figure 5 As shown, Figure 5 A schematic diagram of the structure of a reference voltage output module provided by the present invention.

[0098] It can be seen that in this embodiment, a first reference voltage-dividing resistor and a second reference voltage-dividing resistor are respectively arranged in a one-to-one correspondence between the input end of the voltage follower and the first power supply voltage and the ground, so that the output end of the voltage follower outputs half of the first power supply voltage.

[0099] As an optional embodiment, the subtractor 4 includes a differential amplifier, a first input resistor, a second input resistor, a first feedback resistor and a second feedback resistor, the first end of the first input resistor is connected to the positive output end of the full differential amplifier 2, the second end is respectively connected to the negative phase input end of the differential amplifier and the first end of the first feedback resistor, the second end of the first feedback resistor is connected to the output end of the differential amplifier, the first end of the second input resistor is connected to the negative output end of the full differential amplifier 2, the second end is respectively connected to the positive phase input end of the differential amplifier and the first end of the second feedback resistor, the second end of the second feedback resistor is connected to the output end of the reference voltage output module 3, the power supply end of the differential amplifier is connected to the first power supply voltage, the first input resistor and the second input resistor have the same resistance value, and the first feedback resistor and the second feedback resistor have the same resistance value;

[0100] The first feedback resistor and the second feedback resistor are adjustable resistors.

[0101] Specifically, since the gain of the differential amplifier is the ratio of the feedback resistor to the corresponding input resistor, when the input resistance is constant, the size of the feedback resistor directly affects the gain of the differential amplifier. Generally, the smaller the feedback resistor, the greater the gain. In addition, the feedback resistor also affects the input impedance and output impedance. Increasing the feedback resistor can reduce the input impedance and output impedance, but it will also increase the noise level. Therefore, when designing a differential amplifier, it is necessary to determine the size of the feedback resistor according to the specific application requirements to balance the relationship between gain, impedance and noise. For details, please refer to Figure 6 As shown, Figure 6 A schematic structural diagram of a subtractor provided by the present invention.

[0102] It can be seen that this embodiment uses an adjustable resistor as the first feedback resistor and the second feedback resistor, so that the gain of the differential amplifier can be flexibly adjusted according to requirements to adapt to different application scenarios.

[0103] As an optional embodiment, the first feedback resistor and the second feedback resistor both include:

[0104] A first feedback voltage-dividing resistor, a second feedback voltage-dividing resistor, and finally an Nth feedback voltage-dividing resistor;

[0105] A first switch, a second switch, and so on to an Nth switch, where N is an integer not less than 2;

[0106] The first end of the first switch, the first end of the second switch, and the first end of the Nth switch are connected, and the common end of the connections serves as the first end of the corresponding feedback resistor;

[0107] The second end of the i-th switch is connected to the first end of the i-th feedback voltage-dividing resistor, the second end of the i-th feedback voltage-dividing resistor is connected to the first end of the (i+1)-th feedback voltage-dividing resistor, the second end of the N-th feedback voltage-dividing resistor serves as the second end of the corresponding feedback resistor, and i is a positive integer less than N.

[0108] In this embodiment, each voltage-dividing resistor may be a voltage-dividing resistor with the same resistance value, or may be a voltage-dividing resistor with different resistance values, which may be determined according to actual needs. When the i-th switch is closed, i is a positive integer less than N, the first end of the i-th switch is the first end of the corresponding feedback resistor, the second end of the N-th feedback voltage-dividing resistor is the second end of the corresponding feedback resistor, the resistance value of the feedback resistor is the sum of all the voltage-dividing resistors from the i-th feedback voltage-dividing resistor to the N-th feedback voltage-dividing resistor, and the ratio of the feedback resistor to the corresponding input resistor is the gain of the current differential amplifier.

[0109] For example, if the first feedback resistor and the second feedback resistor include a first feedback voltage divider resistor of 200 kΩ, a second feedback voltage divider resistor of 100 kΩ, a third feedback voltage divider resistor of 50 kΩ, a fourth feedback voltage divider resistor of 50 kΩ, a first switch, a second switch, a third switch, and a fourth switch, and the first input resistor and the second input resistor are both 10 kΩ, then the gain of the differential amplifier is:

[0110] (5);

[0111] Among them, the gain of the differential amplifier is G2, and the adjustable resistor is R GAIN , the input resistance is R.

[0112] When the first switch is closed and the other switches are open, the corresponding adjustable resistor has a resistance of 400kΩ, and the current differential amplifier gain is 40; when the second switch is closed and the other switches are open, the corresponding adjustable resistor has a resistance of 200kΩ, and the current differential amplifier gain is 20; when switch S3 is closed and the other switches are open, the corresponding adjustable resistor has a resistance of 100kΩ, and the current differential amplifier gain is 10; when switch S4 is closed and the other switches are open, the corresponding adjustable resistor has a resistance of 50kΩ, and the current differential amplifier gain is 5. For details, please refer to Figure 7 As shown, Figure 7 A schematic diagram of the structure of an adjustable resistor provided by the present invention.

[0113] It can be seen that in this embodiment, different switches can be closed as required to adjust the resistance value of the corresponding adjustable resistor to change the gain of the differential amplifier to meet the application requirements of different scenarios.

[0114] As an optional embodiment, it also includes:

[0115] The second switch control module is connected to the control ends of the first switch, the second switch, and the Nth switch respectively, and is used to control the on or off of the first switch, the second switch, and the Nth switch.

[0116] In this embodiment, the second switch control module can be used to control the closing / conducting of the above switches to control the gain of the differential amplifier. It should be noted that the second switch control module and the above first switch control module can be one switch control module.

[0117] It can be seen that this embodiment uses the second switch control module to control the closing / conducting of each of the above switches, so as to control the gain of the differential amplifier.

[0118] The present invention further provides a shunt, comprising a bypass resistor and the current detection circuit as described above, wherein two ends of the bypass resistor are connected in parallel with the shunt resistor 1 in the current detection circuit.

[0119] It should be noted that the shunt resistor 1 in the current detection circuit of the present invention is used to measure the current, and the bypass resistor is used to provide a low impedance path to prevent the shunt resistor 1 from being damaged by overheating. The shunt provided by the present invention has the advantages of bidirectional, wide common mode and adjustable gain, thereby realizing accurate control of overcurrent protection, external torque control or commutation using an external controller.

[0120] In addition, the introduction of a shunt provided by the invention can be referred to the embodiment of the above-mentioned current detection circuit, and the invention will not be repeated here.

[0121] It can be seen that the shunt provided in this embodiment provides a reference voltage equal to half of the first power supply voltage to the subtractor 4 through the reference voltage output module 3, so that the absolute value of the voltage across the shunt resistor 1 after two amplifications is less than or equal to half of the first power supply voltage, thereby realizing the measurement of bidirectional current and increasing the application scenarios of current detection.

[0122] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0123] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0124] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A current detection circuit, characterized in that: include: A shunt resistor, wherein the shunt resistor is arranged in the circuit to be tested; A fully differential amplifier, wherein the input end of the fully differential amplifier is connected to the two ends of the shunt resistor, and the output end is connected to the input end of the subtractor, and is used to perform a first-stage amplification on the voltage across the two ends of the shunt resistor to obtain a first output voltage; A reference voltage output module, the output end of which is connected to the reference end of the subtractor, and is used to provide a reference voltage for the subtractor, wherein the reference voltage is half of the first power supply voltage of the subtractor; The subtractor is used to perform secondary amplification on the first output voltage, and obtain a second output voltage based on the secondary amplified voltage and the reference voltage, wherein the second output voltage is less than or equal to the first power supply voltage; Among them, the reference voltage output module provides the subtractor with a reference voltage equal to half of the first power supply voltage, so that the absolute value of the voltage across the shunt resistor after two amplifications is less than or equal to half of the first power supply voltage, thereby realizing the measurement of bidirectional current.

2. The current detection circuit according to claim 1, characterized in that: The input stage module of the fully differential amplifier comprises: Current limiting resistor; A first PMOS transistor, wherein a gate of the first PMOS transistor is connected to a control signal, a source of the first PMOS transistor is connected to a second power supply voltage of the fully differential amplifier, and a drain of the first PMOS transistor is connected to a first end of the current limiting resistor; a second PMOS transistor, wherein the gate of the second PMOS transistor is connected to the first end of the shunt resistor, the source is connected to the second end of the current limiting resistor, and the drain is connected to the first input end of the output stage module of the fully differential amplifier; a third PMOS tube, wherein the gate of the third PMOS tube is connected to the second end of the shunt resistor, the source of the third PMOS tube is connected to the second end of the current limiting resistor, and the drain of the third PMOS tube is connected to the second input end of the output stage module of the fully differential amplifier; The first PMOS tube, the second PMOS tube and the third PMOS tube are all PMOS tubes whose withstand voltage values ​​are greater than a preset voltage value.

3. The current detection circuit according to claim 2, characterized in that: The input stage module of the fully differential amplifier also includes: A fourth PMOS tube, wherein the gate and drain of the fourth PMOS tube are both connected to the second power supply voltage, the source is connected to the gate of the first PMOS tube, and the fourth PMOS tube is an isolated PMOS tube.

4. The current detection circuit according to claim 2, characterized in that: The input stage module of the fully differential amplifier also includes: a first diode, wherein an anode of the first diode is connected to a gate of the second PMOS tube, and a cathode of the first diode is connected to a first end of the current limiting resistor; A second diode, wherein an anode of the second diode is connected to the gate of the third PMOS tube, and a cathode of the second diode is connected to the first end of the current limiting resistor.

5. The current detection circuit according to claim 2, characterized in that: Also includes: A first switch control module, wherein the output end of the first switch control module is connected to the gate of the first PMOS tube, and is used to output the control signal to control whether the fully differential amplifier works.

6. The current detection circuit according to claim 1, characterized in that: The reference voltage output module comprises: A first reference voltage-dividing resistor, a first end of which is connected to the first power supply voltage; a second reference voltage-dividing resistor, wherein a first end of the second reference voltage-dividing resistor is grounded, and a second end of the second reference voltage-dividing resistor is respectively connected to the second end of the first reference voltage-dividing resistor and the input end of the voltage follower, and the first reference voltage-dividing resistor and the second reference voltage-dividing resistor are equal in size; A voltage follower, wherein the output terminal of the voltage follower is connected to the reference terminal of the subtractor.

7. The current detection circuit according to any one of claims 1 to 6, characterized in that: The subtractor includes a differential amplifier, a first input resistor, a second input resistor, a first feedback resistor and a second feedback resistor, wherein the first end of the first input resistor is connected to the positive output end of the fully differential amplifier, and the second end is respectively connected to the negative phase input end of the differential amplifier and the first end of the first feedback resistor, the second end of the first feedback resistor is connected to the output end of the differential amplifier, the first end of the second input resistor is connected to the negative output end of the fully differential amplifier, and the second end is respectively connected to the positive phase input end of the differential amplifier and the first end of the second feedback resistor, the second end of the second feedback resistor is connected to the output end of the reference voltage output module, the power supply end of the differential amplifier is connected to the first power supply voltage, the first input resistor and the second input resistor have the same resistance value, and the first feedback resistor and the second feedback resistor have the same resistance value; The first feedback resistor and the second feedback resistor are adjustable resistors.

8. The current detection circuit according to claim 7, characterized in that: The first feedback resistor and the second feedback resistor both include: A first feedback voltage-dividing resistor, a second feedback voltage-dividing resistor, and finally an Nth feedback voltage-dividing resistor; A first switch, a second switch, and so on to an Nth switch, where N is an integer not less than 2; The first end of the first switch, the first end of the second switch and the first end of the Nth switch are connected, and a common end of the connections serves as a first end of a corresponding feedback resistor; The second end of the i-th switch is connected to the first end of the i-th feedback voltage-dividing resistor, the second end of the i-th feedback voltage-dividing resistor is connected to the first end of the (i+1)-th feedback voltage-dividing resistor, the second end of the N-th feedback voltage-dividing resistor serves as the second end of the corresponding feedback resistor, and i is a positive integer less than N.

9. The current detection circuit according to claim 8, characterized in that: Also includes: The second switch control module is connected to the control ends of the first switch, the second switch, and the Nth switch respectively, and is used to control the on or off of the first switch, the second switch, and the Nth switch.

10. A flow divider, characterized in that: The invention comprises a bypass resistor and the current detection circuit according to any one of claims 1 to 9, wherein two ends of the bypass resistor are connected in parallel with a shunt resistor in the current detection circuit.

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