A hybrid modulation drive system and method for electromagnet

Abstract

The present invention relates to a hybrid modulation drive system and method for an electromagnet, which includes a current sampling resistor, an MCU microprocessor, a PWM generator, a PWM voltage processing unit, a voltage sampling module, a MOS tube, and a DC power supply. The input end of the MCU microprocessor is respectively connected to the current sampling resistor and the voltage sampling module, the output end of the MCU microprocessor is respectively connected to the input end of the MOS tube and the DC power supply, the output end of the PWM generator is connected to the electromagnet coil via the PWM voltage processing unit and the MOS tube, and the output end of the DC power supply is connected to the electromagnet coil. The method performs hybrid modulation within the full range, and when the voltage after PWM rectification is higher than the feedback voltage VFB of the power chip, a DC direct current drive control mode is operated to improve the accuracy of current sampling; when the voltage after rectification is lower than VFB, the PWM drive control is directly used to control the product power under a small current signal.

Description

Technical Field

[0001] The invention relates to a hybrid modulation driving system and a hybrid modulation driving method of an electromagnet. Background Art

[0002] The electromagnet coil drive generally adopts PWM duty cycle drive control scheme or DC direct current drive control scheme. Among them, since the inductance of the coil affects the current change, if the PWM duty cycle adjustment method is used for sampling throughout the entire range, the current sampling accuracy will be limited. Inaccurate current sampling will directly affect the current control, and then affect the control accuracy of the product power; while in the full-scale sampling DC direct current drive control scheme, when the rectified voltage is lower than the power chip feedback voltage VFB, the system will not work, and 12.5% ​​of the current data will not be sampled within the full range, and the product power without current data cannot be controlled. Summary of the invention

[0003] The technical problem to be solved by the present invention is: to provide a hybrid modulation drive system and method for an electromagnet, which improves the current sampling accuracy on the basis of the full-range control of the product power, thereby improving the product power control accuracy. It performs hybrid modulation within the full range, and when the voltage after PWM rectification is higher than the feedback voltage VFB of the power chip, runs the DC direct current drive control mode to improve the current sampling accuracy; when the voltage after rectification is lower than VFB, the electromagnet coil is directly controlled by PWM drive, so that the product power is still controlled under a small current signal.

[0004] The hybrid modulation drive system of the electromagnet comprises a current sampling resistor, an MCU microprocessor, a PWM generator, a PWM voltage processing unit, a voltage sampling module, a MOS tube, and a DC power supply, wherein the input end of the MCU microprocessor is respectively connected to the current sampling resistor and the voltage sampling module, the output end of the MCU microprocessor is respectively connected to the input end of the MOS tube and the DC power supply, the output end of the PWM generator is connected to the electromagnet coil via the PWM voltage processing unit and the MOS tube, and the output end of the DC power supply is connected to the electromagnet coil.

[0005] The current sampling resistor is used to collect the current signal of the electromagnet coil, and convert it into a feedback voltage VFB and send it to the MCU microprocessor; the MCU microprocessor is used to receive the feedback voltage VFB, and compare it with the voltage after PWM rectification, and output the enable signal of the MOS tube / DC power supply according to the comparison result; the PWM generator is used to generate a PWM modulation wave. The PWM voltage processing unit is used to rectify the PWM modulation wave; the voltage sampling module is used to collect the voltage signal after PWM rectification and send it to the MCU microprocessor; the MOS tube is used to conduct the voltage after PWM rectification according to the energy signal of the MCU microprocessor, and drive and control the electromagnet coil; the DC power supply is used to drive and control the electromagnet coil according to the energy signal of the MCU microprocessor.

[0006] In order to achieve filtering, rectification and interference elimination, the PWM voltage processing unit includes an RC three-stage filter and a voltage follower, wherein the output end of the PWM generator is connected to the MOS tube via the RC three-stage filter and the voltage follower in sequence, and the RC three-stage filter is used to filter and rectify the PWM voltage; the voltage follower is used to follow the voltage of the filtered and rectified PWM voltage.

[0007] The hybrid modulation driving method of the electromagnet is implemented by the hybrid modulation driving system of the electromagnet, and specifically includes the following process:

[0008] S1-Judgment: Judgment of the relationship between the feedback voltage VFB and the voltage after PWM rectification

[0009] S2-selection: When the voltage after PWM rectification is higher than the feedback voltage VFB of the power chip, the DC drive control mode is operated; when the voltage after rectification is lower than VFB, the electromagnet coil is directly controlled by PWM drive.

[0010] In order to prevent a drive control idle period, the feedback voltage VFB in process S2 is 0.1-0.5V higher than the actual feedback voltage.

[0011] The present invention discloses a hybrid modulation driving system and method for an electromagnet. On the basis of controlling the full range of product power, the current sampling accuracy is improved, thereby improving the product power control accuracy, and hybrid modulation is performed within the full range. When the voltage after PWM rectification is higher than the feedback voltage VFB of the power chip, a DC direct current driving control mode is operated to improve the current sampling accuracy; when the voltage after rectification is lower than VFB, the electromagnet coil is directly controlled through PWM driving, so that the product power is still controlled under a small current signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The following is a further description of a hybrid modulation drive system of an electromagnet of the present invention in conjunction with the accompanying drawings:

[0013] Figure 1 It is a wireframe diagram of the logic architecture of the hybrid modulation drive system of the electromagnet;

[0014] Figure 2 It is a wireframe diagram of the operation process of the hybrid modulation driving method of the electromagnet;

[0015] Figure 3 It is a sampling waveform diagram of the current sampling resistor in the embodiment of the hybrid modulation drive system of the electromagnet;

[0016] Figure 4 is a voltage waveform diagram of a DC-driven electromagnet coil in the embodiment of the hybrid modulation drive system of the electromagnet;

[0017] Figure 5 It is a voltage waveform diagram of the two ends of the sampling resistor in the PWM driving state in the embodiment of the hybrid modulation driving system of the electromagnet.

[0018] In the figure:

[0019] 1-current sampling resistor, 2-MCU microprocessor, 3-PWM generator, 4-PWM voltage processing unit, 5-voltage sampling module, 6-MOS tube, 7-DC power supply;

[0020] 41-RC three-stage filter, 42-voltage follower. DETAILED DESCRIPTION

[0021] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] In the description of the present invention, it should be understood that the terms "left", "right", "front", "back", "top", "bottom", "inside", "outside", etc., indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0023] The technical solution of the present invention is further described below with specific embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0024] Implementation method 1: Figure 1 As shown, the hybrid modulation drive system of the electromagnet includes a current sampling resistor 1, an MCU microprocessor 2, a PWM generator 3, a PWM voltage processing unit 4, a voltage sampling module 5, a MOS tube 6, and a DC power supply 7, wherein the input end of the MCU microprocessor 2 is respectively connected to the current sampling resistor 1 and the voltage sampling module 5, the output end of the MCU microprocessor 2 is respectively connected to the input end of the MOS tube 6 and the DC power supply 7, the output end of the PWM generator 3 is connected to the electromagnet coil via the PWM voltage processing unit 4 and the MOS tube 6, and the output end of the DC power supply 7 is connected to the electromagnet coil, the current sampling resistor 1 is used to collect the current signal of the electromagnet coil, and convert it into a feedback voltage VFB and send it to the MCU microprocessor 2; the MCU microprocessor 2 is used to receive the feedback voltage VFB, and compare it with the voltage after PWM rectification, and output the enable signal of the MOS tube / DC power supply according to the comparison result; the PWM generator 3 is used to generate a PWM modulation wave. The PWM voltage processing unit 4 is used to rectify the PWM modulated wave; the voltage sampling module 5 is used to collect the voltage signal after PWM rectification and send it to the MCU microprocessor 2; the MOS tube 6 is used to turn on the PWM rectified voltage according to the energy signal of the MCU microprocessor to drive and control the electromagnet coil; the DC power supply 7 is used to drive and control the electromagnet coil according to the energy signal of the MCU microprocessor.

[0025] Specifically for sampling data processing, the current sampling resistor continuously samples the input to the MCU. Under DC mode, 20 numbers are read at any time, and the average value of the 20 numbers is the real current in the electromagnet coil loop; under PWM control, sampling is performed when the PWM high side is fixed, the sampling frequency is set to 15hz, and the timer used is 70ms, that is, 14 samples are taken per second. The sampled values ​​will be stored in a buff, a total of five values, and only the average is taken for the five values. The advantage of fixed high-side sampling is to prevent the data from having both high-side and low-side values, thereby improving data accuracy.

[0026] Implementation 2: The PWM voltage processing 4 unit of the hybrid modulation drive system of the electromagnet includes an RC three-stage filter 41 and a voltage follower 42, wherein the output end of the PWM generator 3 is connected to the MOS tube 6 through the RC three-stage filter 41 and the voltage follower 42 in sequence, and the RC three-stage filter 41 is used to filter and rectify the PWM voltage; the voltage follower 42 is used to follow the voltage of the filtered and rectified PWM voltage. For example, the minimum working voltage of VFB is 0.6V. If it is lower than 0.6V, the DC power supply cannot work. In order to prevent the idle period, the MCU judges the data input by the voltage acquisition module. If U is less than 0.7V, the MCU outputs an enable signal to cut off the work of the DC power supply, and PWM is added to the MOS tube. The system works in the PWM drive control state; if U ≥ 0.7V, the MUC outputs an enable signal to make the DC power supply work normally, and at the same time, the MCU outputs another signal to disconnect the MOS tube and stop working. The system works in the DC drive control state. The remaining structures and components are as described in Implementation 1, and will not be described again.

[0027] Implementation method 3: Figure 2 As shown, the hybrid modulation driving method of the electromagnet is implemented by the hybrid modulation driving system of the electromagnet described in embodiments 1 and 2, and specifically includes the following processes:

[0028] S1-Judgment: Judgment of the relationship between the feedback voltage VFB and the voltage after PWM rectification

[0029] S2-selection: When the voltage after PWM rectification is higher than the feedback voltage VFB of the power chip, the DC drive control mode is operated; when the voltage after rectification is lower than VFB, the electromagnet coil is directly controlled by PWM drive. To prevent the drive control idle period, the feedback voltage VFB is 0.1 to 0.5V higher than the actual feedback voltage.

[0030] Example: Figures 3 to 5 As shown, PWM setting is 100, the current in the loop is 2.13A, the sampling resistance is 0.03R, the voltage of the resistance is 64mV, and the current sampling resistance waveform is as follows Figure 3 As shown in the figure, the voltage waveform at both ends of the electromagnet coil is as follows Figure 4 As shown, the coil circuit adopts DC drive control mode, the current sampling accuracy is high, so the power control accuracy of the product is high; the current is 0.45A, the PWM modulation drive control mode is adopted, and the voltage waveform across the sampling resistor is as follows Figure 5 As shown, the product power is still controlled under small current signals.

[0031] The hybrid modulation drive system and method of the electromagnet improves the current sampling accuracy and thus improves the power control accuracy of the product on the basis of the full-range power control of the product. The hybrid modulation is performed within the full range. When the voltage after PWM rectification is higher than the feedback voltage VFB of the power chip, the DC drive control mode is operated to improve the current sampling accuracy. When the voltage after rectification is lower than VFB, the electromagnet coil is directly controlled by PWM drive, so that the product power is still controlled under small current signals.

[0032] The above description shows the main features, basic principles, and advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments or embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, the above embodiments or embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0033] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A hybrid modulation drive system for an electromagnet, characterized in that: The invention comprises a current sampling resistor (1), an MCU microprocessor (2), a PWM generator (3), a PWM voltage processing unit (4), a voltage sampling module (5), a MOS tube (6), and a direct current power supply (7), wherein the input end of the MCU microprocessor (2) is respectively connected to the current sampling resistor (1) and the voltage sampling module (5), the output end of the MCU microprocessor (2) is respectively connected to the input end of the MOS tube (6) and the direct current power supply (7), the output end of the PWM generator (3) is connected to the electromagnet coil via the PWM voltage processing unit (4) and the MOS tube (6), and the output end of the direct current power supply (7) is connected to the electromagnet coil. The current sampling resistor (1) is used to collect the current signal of the electromagnet coil, and convert it into a feedback voltage VFB and send it to the MCU microprocessor (2); the MCU microprocessor (2) is used to receive the feedback voltage VFB and compare it with the voltage after PWM rectification, and output an enable signal of the MOS tube / DC power supply according to the comparison result; the PWM generator (3) is used to generate a PWM modulation wave; the PWM voltage processing unit (4) is used to rectify the PWM modulation wave; the voltage sampling module (5) is used to collect the voltage signal after PWM rectification and send it to the MCU microprocessor (2); the MOS tube (6) is used to generate a PWM modulation wave according to the MCU The enable signal of the microprocessor turns on the rectified PWM voltage to drive and control the electromagnet coil; the DC power supply (7) is used to drive and control the electromagnet coil according to the enable signal of the MCU microprocessor; the PWM voltage processing (4) unit comprises an RC three-stage filter (41) and a voltage follower (42), wherein the output end of the PWM generator (3) is connected to the MOS tube (6) in sequence via the RC three-stage filter (41) and the voltage follower (42), the RC three-stage filter (41) is used to filter and rectify the PWM voltage; the voltage follower (42) is used to follow the voltage of the filtered and rectified PWM voltage; The driving method of the hybrid modulation driving system of the electromagnet includes the following process: S1-Judgment: Judgment of the relationship between the feedback voltage VFB and the voltage after PWM rectification S2-selection: When the voltage after PWM rectification is higher than the feedback voltage VFB of the power chip, the DC drive control mode is operated; when the voltage after rectification is lower than VFB, the electromagnet coil is directly controlled by PWM drive; the feedback voltage VFB described in process S2 is 0.1~0.5V higher than the actual feedback voltage.

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