Automatic calibration circuit
By designing an automatic calibration circuit and using a constant current source module and a relay module to achieve automatic calibration, the problem of manual correction of the error between the current sampling value and the real value in the prior art is solved, and high-precision current sampling and automatic calibration are achieved, saving production costs and time.
Patent Information
- Application Number
- CN202422173154.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-04
- Publication Date
- 2025-06-27
- Estimated Expiration
- 2034-09-04
AI Technical Summary
The error between the sample value and the true value of the output phase current in the prior art requires manual correction, resulting in increased cost and poor flexibility.
An automatic calibration circuit is designed, including a constant current source module, a relay module, a calibration module and a control module. By controlling the conduction or disconnection of the relay module, the calibration module is automatically calibrated based on the constant current source module.
The driver product's current circuit self-test function is realized, which reduces the need for manual correction, saves production costs and time, improves the accuracy of the current sampling link, and periodically automatically checks the current sampling loop to compensate for errors caused by component aging.
Smart Images
Figure CN223038345U_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the technical field of drive circuit protection and relates to an automatic calibration circuit. Background Art
[0002] In low-power motor driver products, the sampling of the output phase current usually adopts the method of low-side resistance sampling. The principle of this method is to convert the current value into the voltage value across the sampling resistor, and then send the voltage across the sampling resistor to the conditioning circuit (generally composed of devices such as operational amplifiers, bias power supplies, resistors, and capacitors) to obtain a signal with a reasonable amplitude and relatively "clean", and finally send the signal to the ADC (analog-to-digital conversion unit) to convert it into a digital signal for the MCU to use.
[0003] Due to the existence of hardware component errors such as sampling resistor error, bias voltage error, conditioning circuit resistor error, and the error of the ADC itself, this sampling method will cause a large error between the sampling result and the true value. If this error needs to be corrected, usually an external measuring device is used to measure the true value under a certain working condition (with load) and then compare it with the sampling value, that is, manual correction of this error is required. The implementation process of this calibration scheme requires a large amount of labor cost and time cost, and has poor flexibility. Summary of the Invention
[0004] The purpose of this application is to provide an automatic calibration circuit to solve the technical problem that the error between the sampling value and the true value of the output phase current in the prior art needs to be manually corrected, resulting in increased costs.
[0005] To achieve the above object and other related objects, in the first aspect, this application provides an automatic calibration circuit. The automatic calibration circuit includes: a constant current source module, a relay module, a calibration module, and a control module; the relay module is connected to the constant current source module; the calibration module is connected to or disconnected from the constant current source module through the relay module; the control module is connected to the calibration module to control the conduction or disconnection of the relay module, so that the calibration module performs automatic calibration based on the constant current source module.
[0006] In some embodiments of the first aspect of this application, the constant current source module includes: an operational amplifier negative feedback unit, a regulated power supply unit, a high-precision resistor, and a first field-effect transistor; the input end of the operational amplifier negative feedback unit is connected to the regulated power supply unit, and the output end is connected to the gate of the first field-effect transistor; the source of the first field-effect transistor is connected to one end of the high-precision resistor, the drain of the first field-effect transistor is connected to the relay module; the other end of the high-precision resistor is connected to the regulated power supply.
[0007] In some embodiments of the first aspect of the present application, the operational amplifier negative feedback unit includes: an operational amplifier, a second voltage source, and a second resistor; the positive input terminal of the operational amplifier is connected to the regulated power supply unit, and the negative input terminal is connected to the connection line between the source of the first field effect transistor and the high-precision resistor; the positive power supply terminal of the operational amplifier is connected to the voltage source, and the negative power supply terminal is grounded; the output terminal of the operational amplifier is connected to one end of the second resistor, and the other end of the second resistor is connected to the gate of the first field effect transistor.
[0008] In some embodiments of the first aspect of the present application, the regulated power supply unit includes: a first voltage source, a first resistor, and a voltage regulator tube; the positive pole of the first voltage source is connected to the negative pole of the voltage regulator tube, and the negative pole of the first voltage source and one end of the first resistor are commonly grounded; the other end of the first resistor is connected to the positive pole of the voltage regulator tube and the positive input terminal of the operational amplifier negative feedback unit.
[0009] In some embodiments of the first aspect of the present application, the voltage regulator tube uses a high-precision voltage regulator tube.
[0010] In some embodiments of the first aspect of the present application, the calibration module includes: a sampling resistor and a three-phase bridge inverter; one end of the sampling resistor is respectively connected to the relay module and the lower bridge arm of the three-phase bridge inverter, and the other end of the sampling resistor is grounded.
[0011] In some embodiments of the first aspect of the present application, the lower bridge arm of any bridge arm of the three-phase bridge inverter is connected to a sampling resistor.
[0012] In some embodiments of the first aspect of the present application, the control module includes a controller; the controller is connected to the sampling resistor of the calibration module; the controller controls the conduction or disconnection of the relay module so that the calibration module performs automatic calibration based on the constant current source module.
[0013] In some embodiments of the first aspect of the present application, when the calibration module performs automatic calibration based on the constant current source module, it is necessary to collect the zero current sampling value of the sampling resistor in the calibration circuit and the constant current sampling value of the sampling resistor through the controller; when the controller collects the zero current sampling value of the sampling resistor, the relay module is disconnected and the three-phase bridge inverter of the calibration module does not work; when the controller collects the constant current sampling value of the sampling resistor, the relay module is conducted and the three-phase bridge inverter of the calibration module does not work; when the calibration module performs automatic calibration according to the obtained zero current sampling value and the constant current sampling value, the relay module is disconnected and the three-phase bridge inverter of the calibration module is in a working state.
[0014] In some embodiments of the first aspect of the present application, the relay module is in an open state under normal conditions.
[0015] As described above, the automatic calibration circuit of the present application has the following beneficial effects:
[0016] First, based on the above automatic calibration circuit, the driver product of the present application has a function of self-checking the current loop, eliminating the process of manually correcting the current accuracy during the production process, and saving production (labor and time) costs.
[0017] Second, the present application can improve the accuracy of the entire driver current sampling link and reduce the sampling error.
[0018] Third, the automatic calibration circuit of the present application can periodically and automatically check the current sampling loop to compensate for the current sampling error caused by the aging of components during long-term operation. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 It shows a schematic structural diagram of the automatic calibration circuit described in the embodiments of the present application.
[0020] Figure 2 It shows a schematic structural diagram of the constant current source module described in the embodiments of the present application.
[0021] Figure 3 It shows a schematic circuit connection diagram of the automatic calibration circuit described in the embodiments of the present application.
[0022] Figure 4 It shows a schematic circuit connection diagram of the calibration module and the relay module described in the embodiments of the present application.
[0023] DESCRIPTION OF REFERENCE NUMERALS
[0024] 100 Automatic calibration circuit
[0025] 110 Constant current source module
[0026] 111 Operational amplifier negative feedback unit
[0027] 112 Voltage stabilizing power supply unit
[0028] 113 High-precision resistor
[0029] 114 First field effect transistor
[0030] 120 Relay module
[0031] 130 Calibration module
[0032] 140 Control module DETAILED DESCRIPTION OF THE EMBODIMENTS
[0033] The following describes the implementation modes of the present application through specific examples. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific implementation modes. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.
[0034] It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner. Therefore, only the components related to the present application are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.
[0035] In addition, in the present application, descriptions such as "first" and "second" are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present application.
[0036] The present application provides an automatic calibration circuit for three-phase current low-side sampling error based on a constant current source. A constant current source is composed of a reference voltage source, a high-precision resistor, and operational amplifier negative feedback, and the constant current source is introduced into the sampling circuit through a relay or an electronic switch. The microcontroller obtains the sampling values at the zero point and the constant current point by switching the relay and sampling, and uses the two-point correction or multi-point correction method to obtain a linear or piecewise linear calibration curve. This method eliminates the sampling resistor error, welding-induced error, sampling conditioning circuit (resistor) error, as well as the offset and gain error of the ADC through the constant current source calibration method, making the circuit have high precision. This calibration process is automatically completed and takes a very short time (millisecond level), reducing the cost and time of manual calibration in the later stage of product production.
[0037] The following will elaborate on the principle and implementation mode of the automatic calibration circuit of the present application in detail with reference to the drawings, enabling those skilled in the art to understand the automatic calibration circuit of the present application without creative labor.
[0038] The automatic calibration circuit described in this application includes: a constant current source module, a relay module, a calibration module, and a control module; the relay module is connected to the constant current source module; the calibration module is connected to or disconnected from the constant current source module through the relay module; the control module is connected to the calibration module to control the conduction or disconnection of the relay module, so that the calibration module performs automatic calibration based on the constant current source module.
[0039] Please refer to Figure 1 , which shows a schematic structural diagram of the automatic calibration circuit described in an embodiment of this application. As Figure 1 shown, the automatic calibration circuit 100 includes: a constant current source module 110, a relay module 120, a calibration module 130, and a control module 140.
[0040] Specifically, the relay module 120 is connected to the constant current source module 110; the calibration module 130 is connected to or disconnected from the constant current source module 110 through the relay module 120; the control module 140 is connected to the calibration module 130 to control the conduction or disconnection of the relay module 120, so that the calibration module 130 performs automatic calibration based on the constant current source module 110.
[0041] Please refer to Figure 2 and Figure 3 , which respectively show a schematic structural diagram of the constant current source module described in an embodiment of this application and a circuit schematic diagram of the automatic calibration circuit described in an embodiment of this application. As Figure 2 shown, the constant current source module 110 includes: an operational amplifier negative feedback unit 111, a regulated power supply unit 112, a high-precision resistor 113, and a first field effect transistor 114.
[0042] Specifically, the input end of the operational amplifier negative feedback unit 111 is connected to the regulated power supply unit 112, and the output end is connected to the gate of the first field effect transistor 114; the source of the first field effect transistor 114 is connected to one end of the high-precision resistor 113, the drain of the first field effect transistor 114 is connected to the relay module 120; the other end of the high-precision resistor 113 is connected to the regulated power supply unit 112.
[0043] In an embodiment, as Figure 3As shown, the operational amplifier negative feedback unit 111 includes: an operational amplifier U3, a second voltage source V2, and a second resistor R2; the positive input terminal of the operational amplifier U3 is connected to the regulated power supply unit 112, and the negative input terminal is connected to the connection line between the source of the first field effect transistor M1 and the high-precision resistor R4; the positive power supply terminal of the operational amplifier U3 is connected to the second voltage source V2, and the negative power supply terminal is grounded; the output terminal of the operational amplifier U3 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is connected to the gate of the first field effect transistor M1.
[0044] In one embodiment, as Figure 3 shown, the regulated power supply unit 112 includes: a first voltage source V1, a first resistor R1, and a voltage regulator U1; the positive pole of the first voltage source V1 is connected to the negative pole of the voltage regulator U1, and the negative pole of the first voltage source V1 and one end of the first resistor R1 are grounded together; the other end of the first resistor R1 is connected to the positive pole of the voltage regulator U1 and the positive input terminal of the operational amplifier negative feedback unit 111.
[0045] In this embodiment, the voltage regulator U1 is a high-precision voltage regulator.
[0046] Specifically, when the voltage output from the inverting output terminal of the operational amplifier U3 in the operational amplifier negative feedback unit 111 is less than the voltage of the regulated unit 112, since the voltages at the non-inverting terminal and the inverting terminal of the operational amplifier U3 are equivalent, it will force the output voltage of the operational amplifier U3 to increase, thereby causing the output capability of the first field effect transistor M1 to decrease, reducing the current flowing through the first field effect transistor M1, further causing the voltage across the high-precision resistor R4 to decrease, and ultimately increasing the voltage output from the inverting output terminal of the operational amplifier U3;
[0047] In one embodiment, as Figure 3 shown, the calibration module 130 includes: a sampling resistor R3 and a three-phase bridge inverter U2; one end of the sampling resistor R3 is respectively connected to the relay module 120 and the lower bridge arm of the three-phase bridge inverter U2, and the other end of the sampling resistor R3 is grounded.
[0048] Specifically, in this embodiment, only the connection schematic diagram of a group of bridge arms of the three-phase bridge inverter U2 is shown.
[0049] In this embodiment, the lower bridge arm of any bridge arm of the three-phase bridge inverter is connected to a sampling resistor.
[0050] As Figure 4 shown, it shows the connection schematic diagram of the calibration module and the relay module described in one embodiment.
[0051] In this embodiment, it includes a first relay module 120, a second relay module 120, a third relay module 120, a three-phase bridge inverter U3, a first sampling resistor R5, a second sampling resistor R6, and a third sampling resistor R7.
[0052] Specifically, the first relay module 120 is connected to the connection line between the first lower bridge arm of the three-phase bridge inverter U3 and the first sampling resistor R5, the second relay module 120 is connected to the connection line between the second lower bridge arm of the three-phase bridge inverter U3 and the second sampling resistor R6, and the third relay module 120 is connected to the connection line between the third lower bridge arm of the three-phase bridge inverter U3 and the third sampling resistor R7.
[0053] In one embodiment, as Figure 3 shown, the control module 140 includes a controller MCU, and the controller MCU is connected to the sampling resistor of the calibration module 130; the controller MCU controls the conduction or disconnection of the relay module 120 to enable the calibration module 130 to perform automatic calibration based on the constant current source module 110.
[0054] Specifically, when the calibration module 130 performs automatic calibration based on the constant current source module 110, it is necessary to collect the zero-current sampling value of the sampling resistor R3 and the constant-current sampling value of the sampling resistor R3 in the calibration module 130 through the controller MCU; when the controller MCU collects the zero-current sampling value of the sampling resistor R3, the relay module 120 is disconnected and the three-phase bridge inverter U2 of the calibration module 130 does not work; when the controller MCU collects the constant-current sampling value of the sampling resistor R3, the relay module 120 is conducted and the three-phase bridge inverter U2 of the calibration module 130 does not work; when the calibration module 130 performs automatic calibration according to the obtained zero-current sampling value and constant-current sampling value, the relay module 120 is disconnected and the three-phase bridge inverter U2 of the calibration module 130 is in the working state.
[0055] It should be noted that the relay module 120 is in the off state under normal conditions.
[0056] Specifically, when the driver is powered on but not running (i.e., all the bridge arms of the three-phase bridge inverter U2 are disconnected and in a non-operating state), and the relay module 120 is in the off state, the controller MCU collects the zero-current sampling value of the sampling resistor R3 and controls the relay module 120 to close. When the relay module 120 is in the on state and the state of the driver remains unchanged (i.e., the state of the three-phase bridge inverter U2 remains unchanged), the controller MCU collects the constant-current sampling value of the sampling resistor R3 and calculates the true current value of the sampling resistor R3 when the driver is running normally based on the zero-current sampling value and the constant-current sampling value. The true current value is the current value of the driver after error calibration.
[0057] In one embodiment, the timing clock of the controller MCU is set. When the working time of the driver reaches the time preset by the timing clock, an automatic calibration is performed on the driver to avoid the deviation between the sampling value and the true current value of the sampling resistor R3.
[0058] In summary, in the first aspect, based on the above automatic calibration circuit, the driver product of the present application has a current loop self-check function, eliminating the process of manually correcting the current accuracy in the production process and saving production (labor and time) costs. In the second aspect, the present application can improve the accuracy of the entire driver current sampling link and reduce the sampling error. In the third aspect, the automatic calibration circuit of the present application can periodically and automatically verify the current sampling loop and compensate for the current sampling error caused by the aging of components during long-term operation. Therefore, the present application effectively overcomes various disadvantages in the prior art and has high industrial utilization value.
[0059] The above embodiments are only illustrative of the principles and effects of the present application and are not used to limit the present application. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present application should still be covered by the claims of the present application.
Claims
1. An automatic calibration circuit, characterized in that: The circuit comprises: a constant current source module, a relay module, a calibration module and a control module; The relay module is connected to the constant current source module; The calibration module is connected or disconnected with the constant current source module through the relay module; The control module is connected to the calibration module to control the on or off of the relay module, so that the calibration module performs automatic calibration based on the constant current source module.
2. The automatic calibration circuit according to claim 1, characterized in that: The constant current source module includes: an operational amplifier negative feedback unit, a voltage-stabilized power supply unit, a high-precision resistor and a first field effect tube; The input end of the operational amplifier negative feedback unit is connected to the voltage-stabilized power supply unit, and the output end is connected to the gate of the first field effect transistor; The source of the first field effect tube is connected to one end of the high-precision resistor, and the drain of the first field effect tube is connected to the relay module; The other end of the high-precision resistor is connected to the voltage-stabilized power supply unit.
3. The automatic calibration circuit according to claim 2, characterized in that: The operational amplifier negative feedback unit comprises: an operational amplifier, a second voltage source and a second resistor; The positive input terminal of the operational amplifier is connected to the voltage-stabilized power supply unit, and the negative input terminal is connected to the connection line between the source of the first field effect tube and the high-precision resistor; The positive power supply terminal of the operational amplifier is connected to the voltage source, and the negative power supply terminal is grounded; The output end of the operational amplifier is connected to one end of the second resistor, and the other end of the second resistor is connected to the gate of the first field effect transistor.
4. The automatic calibration circuit according to claim 2, characterized in that: The voltage-stabilized power supply unit comprises: a first voltage source, a first resistor and a voltage-stabilizing tube; The positive electrode of the first voltage source is connected to the negative electrode of the voltage regulator tube, and the negative electrode of the first voltage source and one end of the first resistor are grounded together; The other end of the first resistor is connected to the positive electrode of the voltage regulator tube and the positive input end of the operational amplifier negative feedback unit.
5. The automatic calibration circuit according to claim 4, characterized in that: The voltage regulator tube adopts a high-precision voltage regulator tube.
6. The automatic calibration circuit according to claim 1, characterized in that: The calibration module includes: a sampling resistor and a three-phase bridge inverter; One end of the sampling resistor is connected to the relay module and the lower bridge arm of the three-phase bridge inverter respectively, and the other end of the sampling resistor is grounded.
7. The automatic calibration circuit according to claim 6, characterized in that: The lower bridge arm of any bridge arm of the three-phase bridge inverter is respectively connected to one of the sampling resistors.
8. The automatic calibration circuit according to claim 1, characterized in that: The control module includes a controller; The controller is connected to a sampling resistor of the calibration module; The controller controls the relay module to be turned on or off, so that the calibration module performs automatic calibration based on the constant current source module.
9. The automatic calibration circuit according to claim 8, characterized in that: When the calibration module performs automatic calibration based on the constant current source module, the controller needs to collect the zero current sampling value of the sampling resistor in the calibration module and the constant current sampling value of the sampling resistor; When the controller collects the zero current sampling value of the sampling resistor, the relay module is disconnected and the three-phase bridge inverter of the calibration module does not work; When the controller collects the constant current sampling value of the sampling resistor, the relay module is turned on and the three-phase bridge inverter of the calibration module does not work; When the calibration module performs automatic calibration according to the acquired zero current sampling value and the constant current sampling value, the relay module is disconnected and the three-phase bridge inverter of the calibration module is in a working state.
10. The automatic calibration circuit according to claim 9, characterized in that: The relay module is normally in a disconnected state.