Switch linear composite magnet driving circuit

Abstract

The utility model discloses a switch linear composite magnet driving circuit, and belongs to the technical field of electromagnet driving. Which comprises a switch half-bridge circuit composed of a switch tube and a diode, and a load series inductor is connected in the half-bridge switch circuit, and is characterized in that a first current sampling module and a second current sampling module are respectively arranged, and the output end of the first current sampling module and the output end of the second current sampling module are connected with the input end of a PI control module; the output end of the PI control module is connected with the base electrode of the triode, the output end of the second current sampling module is connected with the collector electrode of the triode, the emitter electrode of the triode is connected with the half-bridge switching circuit, the output end of the PI control module is further connected with the controller, the output end of the controller is connected with the control end of the switching tube, and the main circuit current is adjusted by controlling the duty ratio. In the switch linear composite magnet driving circuit, the linear power amplifier is used for current shunting, so that ripple waves are effectively eliminated, and the stability of an electromagnet system is improved.

Description

Technical Field

[0001] The invention discloses a switch linear composite magnet driving circuit, belonging to the technical field of electromagnet driving. Background Art

[0002] Electromagnet is a device that generates electromagnetism when electricity is applied. It is widely used in electromagnetic cranes, magnetic levitation technology, and automation equipment. The magnetic field generated is related to the current size, the number of coil turns, and the ferromagnetic body in the center. The power amplifier can amplify the weak control signal and convert it into current in the coil to generate the required electromagnetic force.

[0003] At present, the mainstream power amplifiers used for electromagnets are divided into the following two types according to their working principles: (1) Linear power amplifiers. Linear power amplifiers have good stability because they work in the linear amplification region, but the transistors are in the amplification state, the DC loss is large, the efficiency is low (usually between 5% and 30%), and the heat generation is serious. (2) Switching power amplifiers. Switching power amplifiers use the on and off properties of MOS tubes and have the advantages of high efficiency, good load adaptability, and large power capacity. However, the output current inevitably has ripples, which cause the electromagnet suction force to fluctuate and lead to instability of the mechanical structure. Therefore, designing a technical solution that can effectively eliminate ripples and improve the stability of the electromagnet system has become an urgent problem to be solved in this field. Utility Model Content

[0004] The technical problem to be solved by the utility model is: to overcome the deficiencies of the prior art and provide a switching linear composite magnet drive circuit which utilizes a linear power amplifier for current shunting, effectively eliminates ripples, improves the stability of the electromagnet system and reduces power consumption.

[0005] The technical solution adopted by the utility model to solve its technical problems is: the switch linear composite magnet drive circuit includes a switch half-bridge circuit composed of a switch tube and a diode, and the load is connected in the half-bridge switch circuit, which is characterized in that: an inductor connected in series with the load is provided, and a first current sampling module and a second current sampling module are respectively provided at both ends of the inductor, the output ends of the first current sampling module and the second current sampling module are connected to the input end of the PI control module, the output end of the PI control module is connected to the base of the transistor, the output end of the second current sampling module is connected to the collector of the transistor, and the emitter of the transistor is connected to the half-bridge switch circuit.

[0006] Preferably, the PI control module includes a subtractor circuit and a PI control circuit, the output ends of the first current sampling module and the second current sampling module are connected to the input end of the subtractor circuit, and the output end of the subtractor circuit is connected to the input end of the PI control circuit.

[0007] Preferably, the output end of the PI control circuit is connected to the base of the transistor through an optocoupler chip.

[0008] Preferably, a first filter module is connected to the output end of the first current sampling module, a second filter module is connected to the output end of the second current sampling module, and the output ends of the first filter module and the second filter module are respectively connected to the PI control module.

[0009] Preferably, the first current sampling module and the second current sampling module use a Hall current sensor of model CC6920.

[0010] Preferably, the switch tube is a MOS tube, and the output end of the controller is connected to the gate of the MOS tube.

[0011] Preferably, the first current sampling module is also connected to the input end of the controller, and the output end of the controller is connected to the control end of the switch tube.

[0012] Compared with the prior art, the utility model has the following beneficial effects:

[0013] In the switch linear composite magnet driving circuit, a linear power amplifier is used for current shunting, which effectively eliminates ripples and improves the stability of the electromagnet system.

[0014] In the first filter module and the second filter module, the signal amplification, high-pass filtering and low-pass filtering functions are integrated and implemented by a differential amplifier circuit, which utilizes the symmetry of the circuit parameters to suppress zero drift, noise and interference. An RC high-pass filter circuit is formed at the input end of the circuit to filter out the DC bias in the input signal; an RC low-pass filter circuit is formed at the output end to filter out the noise in the output signal. Due to the symmetry of the circuit parameters and the negative feedback effect, the differential circuit can significantly amplify the differential mode signal and suppress the common mode signal, and has the ability to suppress zero drift, noise and interference.

[0015] By connecting an optocoupler chip to the output end of the PI control module and converting the voltage signal into a current signal through the optocoupler chip, the current ripple can be eliminated to the greatest extent, while avoiding the influence of the strong current system on the weak current control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the principle block diagram of the switch linear composite magnet drive circuit.

[0017] Figure 2 This is the circuit schematic diagram of the filter module of the switch linear composite magnet drive circuit.

[0018] Figure 3 This is the circuit schematic diagram of the PI control module of the switch linear composite magnet drive circuit. DETAILED DESCRIPTION

[0019] Figures 1 to 3 It is the best embodiment of the utility model, and the following Figures 1 to 3 The utility model is further described.

[0020] like Figure 1 As shown, a switching linear composite magnet driving circuit includes a switching half-bridge circuit composed of MOS tubes T1~T2 and diodes D1~D2, and a load (electromagnet) is connected in the switching half-bridge circuit. In the switching half-bridge circuit, the power supply Vcc is connected to the drain of the MOS tube T1 and the cathode of the diode D2, the source of the MOS tube T1 is connected to the cathode of the diode D1, the anode of the diode D2 is connected to the drain of the MOS tube T2, the source of the MOS tube T2 and the anode of the diode D1 are grounded, one end of the load is connected between the MOS tube T1 and the diode D1, and the other end of the load is connected between the diode D2 and the MOS tube T2.

[0021] An inductor L1 is provided in series with the load, the source of the MOS tube T1 (the cathode of the diode D1) is connected to one end of the inductor L1, the other end of the inductor L1 is connected to one end of the load (electromagnet), and the other end of the load is connected to the anode of the diode D2 (the drain of the MOS tube T2).

[0022] A first current sampling module and a second current sampling module are provided. The input ends of the first current sampling module and the second current sampling module are respectively connected to the two sections of the inductor L1. By providing the inductor L1, the waveform of the current changes from a rectangular wave to a triangular wave after the current passes through the inductor L1, which is more conducive to collecting the current ripple through the second current sampling module.

[0023] The signal output ends of the first current sampling module and the second current sampling module are respectively connected to the input ends of the first filter module and the second filter module, and the output ends of the first filter module and the second filter module are simultaneously connected to the input end of the PI control module. The output end of the second current sampling module is also connected to the collector of the transistor Q1, the output end of the PI control module is connected to the base of the transistor Q1, and the emitter of the transistor Q1 is connected to the anode of the diode D2. In this switch linear composite magnet drive circuit, the first current sampling module and the second current sampling module are implemented using a Hall current sensor of model CC6920. The output end of the first current sampling module is also connected to the signal input end of the single-chip microcomputer (not shown in the figure), and the signal output end of the single-chip microcomputer is connected to the gate of the MOS tube T1~T2. The single-chip microcomputer is implemented using a technical solution known in the art, such as a controller of model STMF103ZET6.

[0024] The first filtering module and the second filtering module are as follows: Figure 2The same circuit structure as shown includes integrated operational amplifiers U1~U2, the output end of the first current sampling module (or the second current sampling module) is connected to one end of the capacitor C1, the other end of the capacitor C1 is simultaneously connected to one end of the resistor R2 and the in-phase input end of the integrated operational amplifier U1, and the other end of the resistor R2 is grounded. The reverse input end of the integrated operational amplifier U1 is simultaneously connected to the resistor R1 and one end of the resistor R3, the other end of the resistor R1 is grounded, and the other end of the resistor R3 is simultaneously connected to the output end of the integrated operational amplifier U1 and one end of the resistor R4.

[0025] The other end of the resistor R4 is connected to one end of the resistor R5 and the in-phase input end of the integrated operational amplifier U2, and the other end of the resistor R5 is grounded. The reverse input end of the integrated operational amplifier U2 is connected to one end of the resistors R6 and R7, and the other end of the resistor R6 is grounded. The other end of the resistor R7 is connected to the output end of the integrated operational amplifier U1 and one end of the resistor R8. The other end of the resistor R8 is connected to one end of the capacitor C2 as the output end of the filter module, and the other end of the capacitor C2 is grounded.

[0026] In the first filter module and the second filter module, the signal amplification, high-pass filtering and low-pass filtering functions are integrated and implemented by a differential amplifier circuit, which utilizes the symmetry of the circuit parameters to suppress zero drift, noise and interference. An RC high-pass filter circuit is formed at the input end of the circuit to filter out the DC bias in the input signal; an RC low-pass filter circuit is formed at the output end to filter out the noise in the output signal. Due to the symmetry of the circuit parameters and the negative feedback effect, the differential circuit can significantly amplify the differential mode signal and suppress the common mode signal, and has the ability to suppress zero drift, noise and interference.

[0027] like Figure 3 As shown, the PI control module includes integrated operational amplifiers U3~U4, the output ends of the first filtering module and the second filtering module are respectively connected to one end of resistors R9~R10, the other end of resistor R9 is simultaneously connected to one end of resistor R11 and the reverse input end of the integrated operational amplifier U3, the other end of resistor R10 is simultaneously connected to resistor R12 and the non-inverting input end of the integrated operational amplifier U4, the other end of resistor R11 is simultaneously connected to one end of resistor R13 and the output end of the integrated operational amplifier U3, and the other end of resistor R12 is grounded.

[0028] The other end of resistor R13 is connected to one end of resistor R15 and the non-inverting input end of integrated amplifier U4, and the other end of resistor R15 is grounded. The output of integrated amplifier U4 is connected to one end of capacitor C3 and pin 1 of optocoupler chip U5, and the other end of capacitor C3 is connected to the reverse input end of integrated amplifier U4 and one end of resistor R14 in series with resistor R16, and the other end of resistor R14 is grounded. Pin 3 of optocoupler chip U5 is connected to the base of transistor Q1, and pin 4 of optocoupler chip U5 is connected to one end of resistor R17, and the other end of resistor R17 is connected to the collector of transistor Q1.

[0029] In the circuit of the PI control module shown above, the voltage values ​​output by the first filter module and the second output module are subtracted by the subtractor circuit composed of the integrated operational amplifier U3 to obtain an error value, and the error value is sent to the PI control circuit composed of the integrated operational amplifier U4. In the PI control module, a general open-loop control system is constructed using PI to directly process the output voltage signal of the subtractor circuit, so that the voltage waveform amplitude reaches a more appropriate value, and then after being converted into a current signal by PC817 (optocoupler chip U5), the current ripple can be eliminated to the greatest extent.

[0030] Since this general open-loop control system is a first-order circuit with only one capacitor and no inductor, the system actually only applies two control methods: proportional and differential.

[0031] The back end of PI control uses an optocoupler for isolation to avoid the influence of the strong power system on the weak power control system. When the input end is powered by a signal, the emitter emits light, and the light receiver generates a photocurrent after receiving the light, which flows out from the output end. Since the signal is transmitted by light, electrical isolation between the input and output ends is achieved. By controlling the voltage between pins 1 and 2 of the optocoupler, the power transistor works in the linear range.

[0032] The specific working process and working principle are as follows:

[0033] For inductive loads such as electromagnets, the current waveform is considered as a DC bias i Ripple current △ i The current of the collector is controlled by controlling the current of the base of the parallel transistor, so that the collector current ic =△ i When the transistor is in the amplification state, the base current controls the collector current. A small signal current is added to the base, causing a large signal current to be output from the collector. ic Will follow ib Linear change, that is ic = β*ib , βIt is the current amplification factor, which indicates the amplification capacity of the transistor.

[0034] This circuit needs to ensure that the transistor works in the linear region. When the voltage applied to the transistor emitter junction is greater than the conduction voltage of the PN junction and is at a certain appropriate value, the transistor emitter junction is forward biased and the collector junction is reverse biased. Therefore, the calculated Urc . ic is the collector current of the power tube, and the ripple current △ i The error value is obtained by subtracting the subtractor circuit in the PI module e , enter the PI control circuit to realize the control of the transistor base current.

[0035] At the same time, the AD sampling channel of the single-chip microcomputer is used to collect the voltage signal output by the PI control module, and the PID algorithm is used to adjust the PWM output duty cycle ARR automatic reload value register to change the switch duty cycle so that the current reaches the preset value.

[0036] In this switch linear composite magnet drive circuit, a linear power amplifier is used for current shunting, which effectively eliminates ripple and improves the stability of the electromagnet system. A high-precision model of system efficiency is derived through staged mathematical modeling. Test results show that compared with the switch power amplifier, the efficiency is only reduced by 7% and the ripple is reduced by 64.32%.

[0037] The above is only the preferred embodiment of the utility model, and does not limit the utility model in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the utility model without departing from the technical solution of the utility model still belongs to the protection scope of the technical solution of the utility model.

Claims

1. A switch linear composite magnet drive circuit, comprising a switch half-bridge circuit composed of a switch tube and a diode, wherein a load is connected to the half-bridge switch circuit, characterized in that: An inductor connected in series with the load is provided, and a first current sampling module and a second current sampling module are respectively provided at both ends of the inductor, the output ends of the first current sampling module and the second current sampling module are connected to the input end of the PI control module, the output end of the PI control module is connected to the base of the transistor, the output end of the second current sampling module is connected to the collector of the transistor, and the emitter of the transistor is connected to the half-bridge switch circuit.

2. The switch linear composite magnet driving circuit according to claim 1, characterized in that: The PI control module includes a subtractor circuit and a PI control circuit. The output ends of the first current sampling module and the second current sampling module are connected to the input end of the subtractor circuit. The output end of the subtractor circuit is connected to the input end of the PI control circuit.

3. The switch linear composite magnet driving circuit according to claim 2, characterized in that: The output end of the PI control circuit is connected to the base of the transistor through an optocoupler chip.

4. The switch linear composite magnet driving circuit according to claim 1, characterized in that: The output end of the first current sampling module is connected to a first filter module, the output end of the second current sampling module is connected to a second filter module, and the output ends of the first filter module and the second filter module are respectively connected to the PI control module.

5. The switch linear composite magnet driving circuit according to claim 1, characterized in that: The first current sampling module and the second current sampling module use a Hall current sensor of model CC6920.

6. The switch linear composite magnet driving circuit according to claim 1, characterized in that: The switch tube is a MOS tube, and the output end of the controller is connected to the gate of the MOS tube.

7. The switch linear composite magnet driving circuit according to claim 1, characterized in that: The first current sampling module is also connected to the input end of the controller, and the output end of the controller is connected to the control end of the switch tube.

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