A pulse constant current source control loop

Abstract

The present invention discloses a pulse constant current source control loop, including a current setting module, a PI regulator, a load, a current sampling module, a channel selector, a preset high level voltage constant input module, and a preset low level voltage constant input module; the high level voltage constant input module, the low level voltage constant input module and the current sampling module are respectively connected to the three input ends of the channel selector, and the output end of the channel selector is connected to the feedback input end of the PI regulator. At the rising edge of the given current, the preset low level is gated; after the gate time count of the preset low level reaches a certain threshold, the sampling current is gated; at the falling edge of the given current, the preset high level is gated; after the gate time count of the preset high level reaches a certain threshold, the sampling current is gated. The present invention can greatly reduce the rise and fall time of the output current, and has a very large promoting effect on improving the accuracy of laser cutting and welding.

Description

Technical Field

[0001] The invention relates to a pulse constant current source, in particular to a pulse constant current source control loop. Background Art

[0002] Pulse constant current sources are widely used in the industrial field and are developing towards intelligence, miniaturization and high integration.

[0003] In the field of laser cutting and welding, the current output characteristics of the pulse constant current source determine the accuracy of laser cutting and welding. Therefore, the pulse constant current source used in the field of laser cutting and welding has strict restrictions on the rise and fall time of the current, which usually needs to be controlled within 30uS.

[0004] like Figure 1 As shown in the figure, it is a block diagram of the conventional pulse constant current source control loop commonly used at present. The PI regulator outputs a current with the same frequency and specific proportional amplitude as the "given current" to the load end according to the given frequency and amplitude of the current, combined with the feedback of current sampling.

[0005] In the field of laser cutting and welding, the current setting is usually a square wave with variable amplitude and frequency, and the frequency range is usually 1-5000Hz. It is required that the current output by the PI regulator must also be a square wave, and the current rise and fall time must be within 30uS.

[0006] Limited by the bandwidth and response speed of the PI regulator, the output current rise and fall time of the pulse constant current source on the market is difficult to reach 30uS, which ultimately reduces the accuracy of laser cutting and welding. Summary of the invention

[0007] The purpose of the present invention is to provide a pulse constant current source control loop, which can significantly reduce the output current rise and fall time of the pulse constant current source.

[0008] The technical solution of the present invention is:

[0009] A pulse constant current source control loop includes a current setting module, a PI regulator, a load, and a current sampling module connected in sequence, and also includes a channel selector, a preset high-level voltage constant input module, and a preset low-level voltage constant input module;

[0010] The output ends of the preset high-level voltage constant input module, the preset low-level voltage constant input module and the current sampling module are respectively connected to the three input ends of the channel selector, and the output end of the channel selector is connected to the feedback input end of the PI regulator.

[0011] Specifically, the current setting module outputs a given current, the current sampling module collects load current and outputs a sampled current; the preset high level voltage constant input module and the preset low level voltage constant input module output a preset high level and a preset low level respectively.

[0012] Preferably, at the rising edge of a given current, the channel selector selects a preset low level; and simultaneously starts the cycle count of the PI regulator to calculate the gating time of the preset low level.

[0013] Preferably, after the PI regulator counts the gate-on time of the preset low level to a certain threshold value △ab, the channel selector turns off the preset low level and gates the sampling current at the same time.

[0014] Preferably, at the falling edge of a given current, the channel selector selects a preset high level; and simultaneously starts the PI regulator cycle count to calculate the selection time of the preset high level.

[0015] Preferably, after the PI regulator counts the gate-on time of the preset high level to a certain threshold value Δcd, the channel selector turns off the preset high level and gates the sampling current at the same time.

[0016] Preferably, as the given current changes, the loop cyclically switches the working state to output a current in phase with the given current.

[0017] The advantages of the present invention are:

[0018] Compared with the traditional pulse constant current source control loop, the present invention can greatly reduce the rise and fall time of the output current, and has a very great promoting effect on improving the accuracy of laser cutting and welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0020] Figure 1 It is a block diagram of an existing pulse constant current source control loop;

[0021] Figure 2 It is a block diagram of the pulse constant current source control loop of the present invention;

[0022] Figure 3 It is a timing diagram of the pulse constant current source control loop of the present invention;

[0023] Figure 4 It is a pulse constant current source control loop output waveform diagram of the present invention;

[0024] Figure 5 It is a waveform diagram of the output current rise time of the pulse constant current source control loop of the present invention;

[0025] Figure 6It is a waveform diagram of the output current falling time of the pulse constant current source control loop of the present invention. DETAILED DESCRIPTION

[0026] like Figure 2 As shown, the pulse constant current source control loop of the present invention includes, in addition to the existing current setting module, PI regulator, load, and current sampling module connected in sequence, a channel selector, a preset high-level voltage constant input module, and a preset low-level voltage constant input module; the output ends of the preset high-level voltage constant input module, the preset low-level voltage constant input module, and the current sampling module are respectively connected to the three input ends of the channel selector, and the output end of the channel selector is connected to the feedback input end of the PI regulator.

[0027] Specifically, the current setting module outputs a given current, the current sampling module collects load current and outputs a sampled current; the preset high level voltage constant input module and the preset low level voltage constant input module output a preset high level and a preset low level respectively.

[0028] The pulse constant current source control loop working process of the present invention is as follows: Figure 3 As shown in the timing diagram, it includes:

[0029] S1. At the rising edge Ta of a given current, the channel selector selects a preset low level, that is, feeds back the preset low level to the PI regulator so that the PI regulator outputs a maximum value at the highest climbing rate; at the same time, the cycle count of the PI regulator is started to calculate the selection time of the preset low level.

[0030] S2. After the PI regulator counts the gate time of the preset low level to a certain threshold value △ab, that is, at time Tb, the channel selector turns off the preset low level and gates the sampling current at the same time, that is, feeds the sampling current back to the PI regulator so that the amplitude of the load current meets the high level of the given current.

[0031] S3. At the falling edge Tc of the given current, the channel selector selects the preset high level, that is, feeds the preset high level back to the PI regulator so that the PI regulator outputs the minimum value at the highest attenuation rate; at the same time, the PI regulator cycle count is started to calculate the selection time of the preset high level.

[0032] S4. After the PI regulator counts the gate time of the preset high level to a certain threshold △cd, that is, at time Td, the channel selector turns off the preset high level and gates the sampling current at the same time, that is, feeds the sampling current back to the PI regulator so that the amplitude of the load current meets the low level of the given current.

[0033] S5. As the given current changes, the loop cyclically switches the S1-S4 working state and outputs a current with the same phase as the given current.

[0034] In the specific implementation, a certain 3KW laser pulse constant current source has a rated input voltage of DC200V, a rated output voltage of DC135V, and a rated output current of 25A. Since the output voltage and current of this 3KW pulse constant current source are high, after being designed and developed according to the conventional control loop, it was tested that the rise and fall time of its output current is much longer than the 30uS required for laser cutting and welding. No matter how the software and hardware parameters of the control loop are adjusted, the required value of 30uS cannot be achieved.

[0035] After the control loop of the 3KW pulse constant current source is rectified according to the solution of the present invention, the values ​​of "preset high level", "preset low level", △ab and △cd are fine-tuned, and the pulse constant current source with improved control loop is used to capture the given current and output current waveforms with an oscilloscope, as shown in FIG. Figure 4 As shown, the output current can accurately follow the given frequency, phase, and proportional amplitude of the current, meeting the requirements of laser cutting and welding. Figure 5 , 6 As shown, the rise and fall time of the output current is about 20uS, which far exceeds the 30uS limit value required for laser cutting and welding.

[0036] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any modifications made according to the spirit of the main technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A pulse constant current source control loop, comprising a current setting module, a PI regulator, a load, and a current sampling module connected in sequence, characterized in that: It also includes a channel selector, a preset high level voltage constant input module, and a preset low level voltage constant input module; The output ends of the preset high-level voltage constant input module, the preset low-level voltage constant input module and the current sampling module are respectively connected to the three input ends of the channel selector, and the output end of the channel selector is connected to the feedback input end of the PI regulator; At the rising edge of a given current, a preset low level is selected to output a maximum value at the highest climbing rate; at the falling edge of a given current, a preset high level is selected to output a minimum value at the highest decay rate.

2. The pulse constant current source control loop according to claim 1, characterized in that: The current setting module outputs a given current, the current sampling module collects load current and outputs a sampled current; the preset high level voltage constant input module and the preset low level voltage constant input module output a preset high level and a preset low level respectively.

3. The pulse constant current source control loop according to claim 2, characterized in that: At the rising edge of a given current, the channel selector selects a preset low level; and simultaneously starts the cycle count of the PI regulator to calculate the selection time of the preset low level.

4. The pulse constant current source control loop according to claim 3, characterized in that: After the PI regulator counts the gate time of the preset low level to a certain threshold value △ab, the channel selector turns off the preset low level and gates the sampling current at the same time.

5. The pulse constant current source control loop according to claim 4, characterized in that: At the falling edge of the given current, the channel selector selects the preset high level; and simultaneously starts the PI regulator cycle count to calculate the selection time of the preset high level.

6. The pulse constant current source control loop according to claim 5, characterized in that: After the PI regulator counts the gate time of the preset high level to a certain threshold value △cd, the channel selector turns off the preset high level and gates the sampling current at the same time.

7. The pulse constant current source control loop according to claim 6, characterized in that: As the given current changes, the loop cyclically switches the working state and outputs a current with the same phase as the given current.

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