A linear magnet power supply based on H-bridge

Abstract

The present invention discloses a linear magnet power supply based on an H-bridge circuit, which consists of a power conversion circuit and a control circuit. The core H-bridge in the power conversion circuit has four bridge arms; the upper bridge arm is used to switch the output current polarity, and the lower bridge arm always works in the linear amplification area to provide current output for the magnet load. The current setting value is given by a high-precision digital-to-analog converter module to ensure high precision and high resolution of the power supply output. The operating voltage of the lower bridge arm of the H-bridge is adjusted by a peripheral control circuit to make it work in the linear area, which is equivalent to a variable resistor. The output current is adjusted by real-time closed-loop feedback of the peripheral control circuit. The invention utilizes the characteristics of the H-bridge structure to achieve bipolar current output, combined with the low ripple noise characteristics of the power device in the linear working area, the power supply system has no high-frequency switching noise, and while realizing the bidirectional switching requirements of the magnet load for the output current, it effectively takes into account the high stability and low ripple magnet load current requirements.

Description

Technical Field

[0001] The present invention relates to a linear magnet power supply based on an H-bridge, and specifically to a method of utilizing an upper half bridge arm in the H-bridge to realize current polarity switching, and a switch device of a lower half bridge arm to operate in a linear amplification region to realize magnet load current magnitude adjustment. Background Art

[0002] In electron storage rings, the correction magnet power supply is an important component for real-time correction of beam position. It poses a challenge to researchers because it requires both fast response speed and high stability. Switching power supplies have the advantage of high efficiency, but because power devices need to work in a high-frequency switching state, they will cause ripple noise interference to the system. The key parameters of the correction magnet power supply are response speed and low output current ripple, and the power level is low, so a linear power supply solution can be used. Usually, linear power supplies need to be equipped with two front-stage DC sources to achieve bipolar output, which increases system cost and control complexity. The H-bridge is widely used in correction magnet power supplies because its power can flow in both directions and can quickly recover load power. At present, the H-bridge topology usually appears in switching power supply application scenarios. Summary of the invention

[0003] The technology of the present invention solves the problem: overcomes the shortcomings of the prior art, starts from the demand for correcting the magnet power supply, combines the advantages of the H-bridge topology and the linear power supply, and proposes a linear magnet power supply design based on the H-bridge, which effectively takes into account the requirements of rapidity and stability of the corrected magnet power supply. The invention utilizes the characteristics of the H-bridge structure that can achieve bipolar current output, combines the low ripple noise characteristics of the power device in the linear working area, and the power supply system has no high-frequency switching noise. While realizing the bidirectional switching requirements of the magnet load for the output current, it effectively takes into account the high stability and low ripple magnet load current requirements.

[0004] The technical solution of the present invention is: a linear magnet power supply based on H-bridge, including a power conversion unit and a control unit. The power conversion unit is centered on the H-bridge and includes a front-stage AC-DC conversion module, an input filter circuit, and an output filter circuit. The control unit includes modules such as current setting, output current sampling, PI closed-loop controller, and a drive circuit for a power device.

[0005] The technical solution adopted by the present invention is: a linear magnet power supply based on an H-bridge, comprising: a power conversion unit and a control unit;

[0006] The power conversion unit includes a sequentially connected front-stage circuit, an H-bridge composed of four switching devices QA, QB, QC and QD, and an output filter circuit, which is used to convert the AC signal of the external power grid into the DC signal required by the magnetic load;

[0007] A control unit, one end of which is connected to the output filter circuit in the power conversion unit for sampling the DC signal, and the other end of which is connected to the H bridge in the power conversion unit for driving and controlling the H bridge, thereby adjusting the DC signal;

[0008] The AC input grid AC signal is rectified and stabilized by the front-stage circuit to obtain the front-stage bus DC signal of the H-bridge. The H-bridge adjusts the output current according to the current setting value and the output current sampling value, where the current setting value is achieved by controlling the digital-to-analog converter AD5791. The H-bridge includes two upper switch devices QA and QC, and two lower switch devices QB and QD. When QA is turned on, QC is turned off, and QD works in the linear adjustment area in the H-bridge, the forward flow of the magnet load current is realized; when QA is turned off, QC is turned on, and QB works in the linear adjustment area in the H-bridge, the reverse flow of the magnet load current is realized. The on-off logic of QA and QC is completed by the control circuit, and the linear drive adjustment of QB and QD is completed by the sampling and current setting value in the control circuit after PI closed-loop adjustment. The output current of the H-bridge adjustment is filtered by the output filter circuit and provided to the magnet load.

[0009] The AC signal of the mains is used to realize the DC power supply of the front stage through the front stage circuit and the input filter circuit. Its output is directly connected to the H-bridge, and the magnet load is powered after the H-bridge power conversion and output filtering. The power switch devices QA and QC on the upper part of the H-bridge switch the output polarity according to the current demand, while the power devices QB and QD on the lower part of the H-bridge always work in the linear amplification area, which is equivalent to a variable resistor. The output current of the H-bridge is adjusted by directly driving the circuit to adjust the voltage through the QB / QD tube in the external control unit. The power conversion unit of the power supply has no high-frequency switching noise. The control unit of the power supply is completed by an analog circuit solution based on a precision operational amplifier. In order to ensure the stability and high precision of the output, the control unit has a PI closed-loop controller, which calculates the output current sampling with the current setting value to achieve precise adjustment of the power device. The current sampling link uses a high-precision current sensor and a current-voltage conversion circuit, and the current setting function is completed by a high-precision digital-to-analog converter (DAC).

[0010] The advantages of the present invention compared with the prior art are:

[0011] (1) In the present invention, the H-bridge structure based on MOSFET is innovatively applied to the linear power supply. The invention combines the advantages of the H-bridge in realizing current polarity switching and the advantages of the linear power supply in fast response and low ripple noise, providing ideas for the design of a low-power fast correction magnet power supply. At present, the H-bridge is commonly used for power conversion in switching power supplies. The four switching devices in the H-bridge all work in a continuous on and off state, and the output power conversion is achieved by adjusting the duty cycle of the switching device drive signal. In the present invention, the advantage of the H-bridge in realizing output current polarity switching is utilized, but the device for realizing power conversion works in the linear region, which is equivalent to a variable resistor, avoiding the introduction of switching noise, and can effectively reduce the output current ripple of the power supply and improve the power supply performance.

[0012] (2) In the present invention, a 20-bit digital-to-analog converter AD5791 is used as the current setting value, which avoids the limitation of the output current regulation resolution of the traditional H-bridge switching power supply by the regulation step size of the digital drive signal of the switching device, thereby ensuring the regulation resolution of the power supply output current.

[0013] (3) The power supply designed by the present invention is tested using a magnetic load, and the long-term stability of the output current is better than 20ppm, the output current resolution is better than 20ppm, and the frequency response bandwidth of the power supply to a 10kHz sine wave meets the requirement of -3dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of a linear magnet power supply based on an H-bridge of the present invention;

[0015] Figure 2 It is the control circuit scheme of the upper arm of the H bridge in the present invention;

[0016] Figure 3 It is the control circuit scheme of the lower bridge arm of the H bridge in the present invention;

[0017] Figure 4 It is a power supply response bandwidth test diagram measured in the present invention;

[0018] Figure 5 It is a test diagram of the long-term stability of the power supply measured in the embodiment of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0020] like Figure 1As shown, a linear magnet power supply based on an H-bridge of the present invention comprises: a power conversion unit and a control unit. The power conversion unit comprises an AC input, a pre-stage circuit, an H-bridge composed of four switching devices QA, QB, QC and QD connected in sequence (not marked in the figure), and an output filter circuit, which is used to convert the AC signal of the external power grid into a DC signal required by the magnet load; one end of the control unit is connected to the output filter circuit in the power conversion unit for sampling the DC signal, and the other end is connected to the H-bridge in the power conversion unit for driving and controlling the H-bridge, thereby adjusting the DC signal.

[0021] The AC input grid AC signal is rectified and stabilized by the front-stage circuit to obtain the front-stage bus DC signal of the H-bridge. The H-bridge adjusts the output current according to the current setting value and the output current sampling value, where the current setting value is achieved by controlling the digital-to-analog converter AD5791. The H-bridge includes two upper switch devices QA and QC, and two lower switch devices QB and QD. When QA is turned on, QC is turned off, and QD works in the linear adjustment area in the H-bridge, the forward flow of the magnet load current is realized; when QA is turned off, QC is turned on, and QB works in the linear adjustment area in the H-bridge, the reverse flow of the magnet load current is realized. The on-off logic of QA and QC is completed by the control circuit, and the linear drive adjustment of QB and QD is completed by the sampling and current setting value in the control circuit after PI closed-loop adjustment. The output current adjusted by the H-bridge is filtered by the output filter circuit and provided to the magnet load.

[0022] The embodiment of the present invention provides a linear magnet power supply based on H-bridge and a control method thereof. A linear magnet power supply with a rated output power of 300W was developed, and the power conversion unit consists of a front-stage AC-DC circuit, an input filter circuit module, an H-bridge, and an output filter circuit module. The AC-DC module adopts the RSP-750-48V power supply module produced by Mean Well, which supplies 90-264VAC (47-63Hz), outputs 48V (outputs 40-110% rated voltage through external voltage regulation), has an efficiency of ≥92%, has overvoltage and overcurrent protection and meets relevant electromagnetic compatibility standards. The H-bridge power device uses MOSFET, which is a current-type full-bridge inverter with four bridge arms, which can be regarded as two half-bridges. The bridge arms QA and QD are used as positive current outputs, and the bridge arms QB and QC are used as negative current outputs. And the output filter parameters are calculated. The control unit uses the STM32 controller chip to realize the drive control of the current sampling chip ADC, the current setting chip DAC, and the external communication interface chip.

[0023] Since the lower bridge arms QB and QD of the H-bridge always work in the linear amplification region, PWM control is not required. Instead, the analog voltage value provided by AD5791 is used as the current setting value. The system's PI closed-loop regulation circuit and the drive control circuit of the four power devices are implemented using analog circuit solutions. The analog control circuit is based on a high-precision operational amplifier, such as Figure 2 The figure shows the control circuit of the upper arm QA and QC of the H-bridge. The positive and negative current setting values ​​determine the opening and closing of the upper tubes QA and QC. When the current setting value is greater than 0, the upper tube QA is turned on (logically opposite to the QC signal) after being amplified 50 times in phase, the comparator, the gate circuit, the current amplifier, and the isolation driver, and the output is positive; when the current setting value is less than 0, the upper tube QC is turned on (logically opposite to the QA signal) after being amplified 50 times in phase, the comparator, the gate circuit, the current amplifier, and the isolation driver, and the output is negative.

[0024] like Figure 3 The figure shows the control drive circuit of the lower arm QB and QD of the H-bridge. The error between the output sampling current and the current setting value is amplified 100 times. After the difference is dynamically adjusted, the drive voltage of QB and QD is linearly controlled by the voltage amplifier and the current amplifier. The current amplifier is a current output type emitter follower that can directly drive the gate of the MOSFET.

[0025] Use the developed power supply and load for testing. Figure 4 To test the system's response characteristics to a 10kHz input sine wave, ref Set the waveform for the current, i o The output current waveform of the power supply has an amplitude attenuation of about -1.41dB and a phase shift of about 36.29°. It is the long-term operation stability test result when the power supply outputs 3A. The ordinate is the output current value and the abscissa is time. DCCT refers to the current sensor. DCCT is often used for scaling when measuring large currents. It can be seen from the figure that the output current stability of the power supply can reach 5ppm for 8 hours.

[0026] It can be seen from the results that the present invention can effectively take into account the requirements of rapidity and stability of the correction magnet power supply.

[0027] The above is a detailed introduction to a linear magnet power supply based on an H-bridge and a control method thereof provided in an embodiment of the present invention. The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technical personnel in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A linear magnet power supply based on an H-bridge, characterized in that: include: Power conversion unit and control unit; The power conversion unit includes a sequentially connected front-stage circuit, an H-bridge composed of four switching devices QA, QB, QC and QD, and an output filter circuit, which is used to convert the AC signal of the external power grid into the DC signal required by the magnetic load; A control unit, one end of which is connected to the output filter circuit in the power conversion unit for sampling the DC signal, and the other end of which is connected to the H bridge in the power conversion unit for driving and controlling the H bridge, thereby adjusting the DC signal; The AC input grid AC signal is rectified and stabilized by the front-stage circuit to obtain the front-stage bus DC signal of the H-bridge. The H-bridge adjusts the output current according to the current setting value and the output current sampling value, wherein the current setting value is realized by controlling the digital-to-analog converter AD5791. The H-bridge includes two upper switch devices QA and QC, and two lower switch devices QB and QD. When QA is turned on, QC is turned off, and QD works in the linear adjustment area in the H-bridge, the forward flow of the magnet load current is realized; when QA is turned off, QC is turned on, and QB works in the linear adjustment area in the H-bridge, the reverse flow of the magnet load current is realized. The on-off logic of QA and QC is completed by the control circuit, and the linear drive adjustment of QB and QD is completed after PI closed-loop adjustment of the sampling and current setting value in the control circuit. The output current adjusted by the H-bridge is filtered by the output filter circuit and provided to the magnet load.

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