1 Introduction It is necessary to design and develop a high-power industrial laser pulse power supply with high reliability, small size and low cost. The main technical requirements are as follows: input power supply phase AC 380, output voltage of 4007 or less adjustable output current maximum 300 Output frequency 100 The following adjustable output pulse width 0.120 According to this requirement, we chose a small-capacity switching power supply charging, large-capacity capacitor energy storage, to achieve high-power pulse discharge design. According to this scheme, the design of the switching power supply for charging becomes the core content of the entire power supply design. A lot of research and test work has been carried out in the design process, and many of them have a lot of experience. Now I have a little experience in the selection of devices in the design process of switching power supply for charging.
2 Main circuit In the past industrial or medical laser equipment, the power devices were mostly thyristors. Due to the low switching frequency of the thyristor, the dynamic response time of the power supply is long and the regulation performance is poor. Moreover, the conduction of the thyristor depends mainly on the change of the trigger phase angle, so it is difficult to realize the closed-loop control of the system. Fluctuation is also easy to affect its stability; in addition, the low switching frequency of the thyristor causes the capacitors and capacitors in the circuit to be reset in a large volume, which makes the whole system bulky. In addition, the peripheral discrete devices are more The reliability is unfavorable.
With the rapid development of frequency power devices, the performance is stable, and the high-power 81-insulated bipolar transistors with high speed integration are more and more widely used in the field of power electronics technology. It has the advantages of a voltage-controlled high-speed switch from 71 and a low-on-voltage drop of 18, making it the best power electronic switching device in medium power applications to date. According to the investigation and the experience of previous work, in order to meet the user's requirements for power supply reliability and volume and weight, we decided to use the power circuit as the main circuit of the power supply.
Since the power supply adopts 380, phase AC power supply, if the voltage fluctuation of the grid ± is considered, the voltage variation range after rectified chopping is about 470,570. In addition, the inverter circuit adopts a full bridge type to prevent the bridge arm from passing through. There must be enough working dead time. If the maximum working duty ratio is 0.9, the frequency transformer ratio is 1. According to the power requirement of the pulse discharge, the system full power output is 400. During operation, the on-state average of 81 in the inverter circuit The current is 20 six, the peak current inverter operating frequency is 20 pun 2, and the output reactor is 1 bas., the AC component peak of the reactor has a peak value of 3.75 to 21.875.
Therefore, in order to retain sufficient safety margin, 8 of 12007504 should be used. The actual application of the device is Japan Rhom Corporation with this rating, 100 2 sen series double unit 168 butyl module.
3 The performance of the driver circuit of the driver circuit has a great influence on whether the 1681 can exert the best effect. We have a deep experience in the practice process.
Ding is a voltage-controlled device with a maximum input resistance of several tens of megaohms. Taking 500 2 cents as our example, when the 0-pole driving voltage is 2, the maximum value of the static driving current is less than 0.5, so it is easy to realize its driving. However, in fact, there is parasitic capacitance between the terminals of the D. Therefore, the load of the driving circuit is actually a capacitive network. To achieve high-speed switching, the driving circuit must be able to quickly provide enough turn-on trigger charge and turn-off absorbed charge. That is, to provide a high enough switching instantaneous current to operate at a voltage of 600, the required switching charge can be up to 400. If it is to be turned on within 500, 1 must be turned off, then drive the circuit during the turn-on time. The absorption current should not be lower than 0.4; considering that the turn-on voltage threshold can be as high as 7.5 and the minimum can reach 4.57, the driving capability of the driving circuit is quite high. At the same time, too fast switching speed may cause a safe working area with working conditions exceeding 108, especially in the case of short-circuit over-current, the speed shutdown is easy to cause, 1 damage, and therefore can not improve the driving circuit Drive capability. In short, the design of the driver circuit is quite complicated. Although there are already commercial integrated drivers, we still have some troubles in the selection process.
After careful analysis, the final reason for the fault is that the 841 drive circuit 4.5 is turned off, and the turn-off drive voltage cannot guarantee a reliable turn-off of 8 in some cases.
In theory, the 1081 is zero voltage shutdown, but in practical hard-switched full-bridge inverter circuits, zero voltage shutdown is unreliable in many cases. In particular, when 108 is turned off or the other arm is turned on, the voltage between the electrodes is increased by the capacitor, and the interelectrode capacitor is charged to form a positive voltage spike between the poles. Take the elbow 5002 as an example. When a voltage is 10, the maximum transfer capacitance can reach 3. At this time, only a very low voltage-to-zero voltage rise rate is required, and the drive circuit is required to provide a large transfer capacitance. The current is absorbed to ensure reliable shutdown of the 1081. There are two ways to increase the current absorption capability of the drive circuit, which is to reduce the drive resistance scale 8, but this will speed up the 108 turn-off speed, increase the voltage rise rate between the CE poles, and increase the charge current of the transfer capacitor. Another way is to reduce the shutdown drive voltage. Although the 841 provides a shutdown drive voltage of 4.5, we still have misleading questions during the actual use. Therefore, we replaced the drive circuit with the drive circuit 57959 produced by Nippon Diamond Co., Ltd. The drive drive voltage of the drive is lOV. In the case where the other performances are basically the same, it is clear that for the practical application of the same, the turn-off driving voltage of 1 is much more reliable than 4.57. The test proved that it did solve 108 misleading questions.
4 control circuit control circuit mainly realizes the function of human-machine dialogue and the generation and transmission of internal real-time control signals. The main difference between a switching power supply for a laser and an ordinary switching power supply is that the load of the former is a non-linear load, so the former is more complicated than the latter in the design of the control circuit. In the control process, a lot of calculations are needed, which is difficult to implement with analog devices. Therefore, we decided to use a single-chip microcomputer for digital real-time control.
The company's 106072, 10 series MCU adopts Harvard bus structure, which is fast and flexible, and is very suitable for use as an embedded microcontroller. At present, it has been widely used in China and has sufficient technical support. Among them, 16072 itself has 28 bytes of program memory, 128 bytes of data registers, 5 channels and 8 bits, conversion channel, 1 port machine 1 output channel, 1 channel 52 standard serial bus channel, the above channels can be used as universal 10 ports are used, in addition to 13 universal 10 ports, fully functional, can complete the power supply design. We need to use a total of 101,672 in the whole control system. Among them, the system is the system host, and the man-machine dialogue function is realized. As the voltage loop controller completes the 0 conversion of the input and output voltage, the calculation of the initial output pulse width and the communication with the main control chip as the current loop controller to complete the output current of the 0 conversion, the final pulse width calculation and single channel, machine Output. The analog signal is detected and isolated by the Hall sensor, filtered by the hardware circuit and then converted into a digital signal by a built-in 0 converter. The frequency division operation is completed by the hardware circuit and forms two control signals with a phase difference of 180, which are respectively used to control the two bridge arms of the full bridge converter. To strengthen the control circuit coupling away.
In the main circuit current and voltage detection, because the detection signal is not common, and there is no direct electrical connection between the control circuit and the main circuit, and in order to ensure reliability and detection slightly, we choose the magnetic balance type Voltage sensor module. This module can achieve good electrical separation between the main circuit and the control circuit, and has excellent dynamic performance and measurement accuracy. It is an excellent current and voltage sensor for power electronics. As a result of the use, the sensor has stable performance and high reliability.
5 protection circuit protection circuit is indispensable in the switching power supply, good protection circuit mainly includes over-voltage protection and over-current protection. In the shutdown process, the energy stored in the stray inductance should be released, it will be at 108. A high voltage spike is generated between the 1 poles. To absorb or suppress this spike. A common method is to add a buffer circuit to each switch. However, in our design practice, it has been found that many of these 8, snubber circuits have increased the complexity of the system during our testing. This type of buffer circuit has failed many times, and the effect of increasing reliability is that this method does not reduce the total loss of the circuit. The loss that is reduced in 8 actually shifts to the buffer circuit. Through analysis, we believe that 5002, the rated working voltage is 12007, far greater than the actual maximum operating voltage of 600, the actual maximum loss is about 150 is also much smaller than the allowable space itself, there is parasitic capacitance, and added anti-parallel fast recovery pole The tube reverse recovery time is less than 25,1!5. When the bridge arm is buckled 81 and the inter-electrode voltage is higher than the input voltage, the inter-electrode voltage can be clamped to the input through the anti-parallel pole tube on the other bridge arm. On the voltage, therefore, we decided to cancel the ruler, the snubber circuit, only in the system, 9= then the factory uses the above formula, we can solve the problem from the idea of ​​the magnetic circuit. The specific idea is as follows to separate the time 1 into a small segment. During this time period, the movement speed of the vortex disk is linearly changed, and the path of motion within 1 can be obtained. At each motion time interval, corresponding to the distance between the eddy current disk and the coil, corresponding to the air gap permeability, the magnetic path can be solved by the magnetic circuit equation, and the magnetic field can be obtained by the Maxwel formula or 4. Force, corresponding to the dynamic differential equations listed and solved to obtain the entire dynamic characteristics.
4 Analysis and calculation results According to the design of the electric repulsion mechanism of the DC breaker Circuit Breaker, the calculation result is 2.
1 Guan Shengbian. Electrical engineering. Mechanical Industry Press, 976 Fei Hongjun, Zhang Guansheng. Dynamic analysis and calculation of electrical institutions.
Mechanical Industry Edition, 993 3 weeks gram. Engineering electromagnetic field monograph. Huazhong Institute of Technology published 41 Sheng Jianhuo and so on. Electromagnetic field quality analysis. Science Press, connected to the DC input terminal of the 108 Dinverter Bridge parallel connected to the non-inductive absorption capacitor.
Theoretical calculations and test results show that the transformer leakage inductance is about 1诎 at full load shutdown, and the voltage spike generated on the absorption capacitor 0.15108 is less than 600 during the dead zone, and the additional oscillation is very slight. Hundred kilohertz, the peak voltage is lower than 20V, the peak current is lower than 10, and the attenuation is very fast, which has no effect on the circuit operation, so in fact, in our case, the 0 buffer circuit can be no longer added.
For short-circuit overcurrent protection, according to the characteristics of 81, the protection off time is too long or too short. Although the driver M57959L has overcurrent detection and slow shutdown protection, its overcurrent detection response time is 10 old, which cannot protect against short pulse overcurrent. Therefore, we did not use the M57959L overcurrent detection function.
This function is implemented by an additional circuit to detect the current signal by the Hall sensor and remove the interference signal through filtering, and then compare the signal through the comparator, if an overcurrent occurs. Bay, maintain overcurrent 2 old adjustable lock, and high-speed optocoupler to set the M57959L overcurrent detection terminal to a high level, through the 55795 hole overcurrent slow turn-off function to achieve short pulse overcurrent protection.
6 Conclusion In the design of switching power supply, the rational selection of important devices is very important. Only a large number of tuning, research, mastering the parameter characteristics of various devices, and after a comprehensive and comprehensive trade-off, can rationally select the device. This article only describes the author's practical experience in the actual development of laser switching power supply. Due to space limitations, the selection of power supply circuit components will not be repeated.
2 Main circuit In the past industrial or medical laser equipment, the power devices were mostly thyristors. Due to the low switching frequency of the thyristor, the dynamic response time of the power supply is long and the regulation performance is poor. Moreover, the conduction of the thyristor depends mainly on the change of the trigger phase angle, so it is difficult to realize the closed-loop control of the system. Fluctuation is also easy to affect its stability; in addition, the low switching frequency of the thyristor causes the capacitors and capacitors in the circuit to be reset in a large volume, which makes the whole system bulky. In addition, the peripheral discrete devices are more The reliability is unfavorable.
With the rapid development of frequency power devices, the performance is stable, and the high-power 81-insulated bipolar transistors with high speed integration are more and more widely used in the field of power electronics technology. It has the advantages of a voltage-controlled high-speed switch from 71 and a low-on-voltage drop of 18, making it the best power electronic switching device in medium power applications to date. According to the investigation and the experience of previous work, in order to meet the user's requirements for power supply reliability and volume and weight, we decided to use the power circuit as the main circuit of the power supply.
Since the power supply adopts 380, phase AC power supply, if the voltage fluctuation of the grid ± is considered, the voltage variation range after rectified chopping is about 470,570. In addition, the inverter circuit adopts a full bridge type to prevent the bridge arm from passing through. There must be enough working dead time. If the maximum working duty ratio is 0.9, the frequency transformer ratio is 1. According to the power requirement of the pulse discharge, the system full power output is 400. During operation, the on-state average of 81 in the inverter circuit The current is 20 six, the peak current inverter operating frequency is 20 pun 2, and the output reactor is 1 bas., the AC component peak of the reactor has a peak value of 3.75 to 21.875.
Therefore, in order to retain sufficient safety margin, 8 of 12007504 should be used. The actual application of the device is Japan Rhom Corporation with this rating, 100 2 sen series double unit 168 butyl module.
3 The performance of the driver circuit of the driver circuit has a great influence on whether the 1681 can exert the best effect. We have a deep experience in the practice process.
Ding is a voltage-controlled device with a maximum input resistance of several tens of megaohms. Taking 500 2 cents as our example, when the 0-pole driving voltage is 2, the maximum value of the static driving current is less than 0.5, so it is easy to realize its driving. However, in fact, there is parasitic capacitance between the terminals of the D. Therefore, the load of the driving circuit is actually a capacitive network. To achieve high-speed switching, the driving circuit must be able to quickly provide enough turn-on trigger charge and turn-off absorbed charge. That is, to provide a high enough switching instantaneous current to operate at a voltage of 600, the required switching charge can be up to 400. If it is to be turned on within 500, 1 must be turned off, then drive the circuit during the turn-on time. The absorption current should not be lower than 0.4; considering that the turn-on voltage threshold can be as high as 7.5 and the minimum can reach 4.57, the driving capability of the driving circuit is quite high. At the same time, too fast switching speed may cause a safe working area with working conditions exceeding 108, especially in the case of short-circuit over-current, the speed shutdown is easy to cause, 1 damage, and therefore can not improve the driving circuit Drive capability. In short, the design of the driver circuit is quite complicated. Although there are already commercial integrated drivers, we still have some troubles in the selection process.
After careful analysis, the final reason for the fault is that the 841 drive circuit 4.5 is turned off, and the turn-off drive voltage cannot guarantee a reliable turn-off of 8 in some cases.
In theory, the 1081 is zero voltage shutdown, but in practical hard-switched full-bridge inverter circuits, zero voltage shutdown is unreliable in many cases. In particular, when 108 is turned off or the other arm is turned on, the voltage between the electrodes is increased by the capacitor, and the interelectrode capacitor is charged to form a positive voltage spike between the poles. Take the elbow 5002 as an example. When a voltage is 10, the maximum transfer capacitance can reach 3. At this time, only a very low voltage-to-zero voltage rise rate is required, and the drive circuit is required to provide a large transfer capacitance. The current is absorbed to ensure reliable shutdown of the 1081. There are two ways to increase the current absorption capability of the drive circuit, which is to reduce the drive resistance scale 8, but this will speed up the 108 turn-off speed, increase the voltage rise rate between the CE poles, and increase the charge current of the transfer capacitor. Another way is to reduce the shutdown drive voltage. Although the 841 provides a shutdown drive voltage of 4.5, we still have misleading questions during the actual use. Therefore, we replaced the drive circuit with the drive circuit 57959 produced by Nippon Diamond Co., Ltd. The drive drive voltage of the drive is lOV. In the case where the other performances are basically the same, it is clear that for the practical application of the same, the turn-off driving voltage of 1 is much more reliable than 4.57. The test proved that it did solve 108 misleading questions.
4 control circuit control circuit mainly realizes the function of human-machine dialogue and the generation and transmission of internal real-time control signals. The main difference between a switching power supply for a laser and an ordinary switching power supply is that the load of the former is a non-linear load, so the former is more complicated than the latter in the design of the control circuit. In the control process, a lot of calculations are needed, which is difficult to implement with analog devices. Therefore, we decided to use a single-chip microcomputer for digital real-time control.
The company's 106072, 10 series MCU adopts Harvard bus structure, which is fast and flexible, and is very suitable for use as an embedded microcontroller. At present, it has been widely used in China and has sufficient technical support. Among them, 16072 itself has 28 bytes of program memory, 128 bytes of data registers, 5 channels and 8 bits, conversion channel, 1 port machine 1 output channel, 1 channel 52 standard serial bus channel, the above channels can be used as universal 10 ports are used, in addition to 13 universal 10 ports, fully functional, can complete the power supply design. We need to use a total of 101,672 in the whole control system. Among them, the system is the system host, and the man-machine dialogue function is realized. As the voltage loop controller completes the 0 conversion of the input and output voltage, the calculation of the initial output pulse width and the communication with the main control chip as the current loop controller to complete the output current of the 0 conversion, the final pulse width calculation and single channel, machine Output. The analog signal is detected and isolated by the Hall sensor, filtered by the hardware circuit and then converted into a digital signal by a built-in 0 converter. The frequency division operation is completed by the hardware circuit and forms two control signals with a phase difference of 180, which are respectively used to control the two bridge arms of the full bridge converter. To strengthen the control circuit coupling away.
In the main circuit current and voltage detection, because the detection signal is not common, and there is no direct electrical connection between the control circuit and the main circuit, and in order to ensure reliability and detection slightly, we choose the magnetic balance type Voltage sensor module. This module can achieve good electrical separation between the main circuit and the control circuit, and has excellent dynamic performance and measurement accuracy. It is an excellent current and voltage sensor for power electronics. As a result of the use, the sensor has stable performance and high reliability.
5 protection circuit protection circuit is indispensable in the switching power supply, good protection circuit mainly includes over-voltage protection and over-current protection. In the shutdown process, the energy stored in the stray inductance should be released, it will be at 108. A high voltage spike is generated between the 1 poles. To absorb or suppress this spike. A common method is to add a buffer circuit to each switch. However, in our design practice, it has been found that many of these 8, snubber circuits have increased the complexity of the system during our testing. This type of buffer circuit has failed many times, and the effect of increasing reliability is that this method does not reduce the total loss of the circuit. The loss that is reduced in 8 actually shifts to the buffer circuit. Through analysis, we believe that 5002, the rated working voltage is 12007, far greater than the actual maximum operating voltage of 600, the actual maximum loss is about 150 is also much smaller than the allowable space itself, there is parasitic capacitance, and added anti-parallel fast recovery pole The tube reverse recovery time is less than 25,1!5. When the bridge arm is buckled 81 and the inter-electrode voltage is higher than the input voltage, the inter-electrode voltage can be clamped to the input through the anti-parallel pole tube on the other bridge arm. On the voltage, therefore, we decided to cancel the ruler, the snubber circuit, only in the system, 9= then the factory uses the above formula, we can solve the problem from the idea of ​​the magnetic circuit. The specific idea is as follows to separate the time 1 into a small segment. During this time period, the movement speed of the vortex disk is linearly changed, and the path of motion within 1 can be obtained. At each motion time interval, corresponding to the distance between the eddy current disk and the coil, corresponding to the air gap permeability, the magnetic path can be solved by the magnetic circuit equation, and the magnetic field can be obtained by the Maxwel formula or 4. Force, corresponding to the dynamic differential equations listed and solved to obtain the entire dynamic characteristics.
4 Analysis and calculation results According to the design of the electric repulsion mechanism of the DC breaker Circuit Breaker, the calculation result is 2.
1 Guan Shengbian. Electrical engineering. Mechanical Industry Press, 976 Fei Hongjun, Zhang Guansheng. Dynamic analysis and calculation of electrical institutions.
Mechanical Industry Edition, 993 3 weeks gram. Engineering electromagnetic field monograph. Huazhong Institute of Technology published 41 Sheng Jianhuo and so on. Electromagnetic field quality analysis. Science Press, connected to the DC input terminal of the 108 Dinverter Bridge parallel connected to the non-inductive absorption capacitor.
Theoretical calculations and test results show that the transformer leakage inductance is about 1诎 at full load shutdown, and the voltage spike generated on the absorption capacitor 0.15108 is less than 600 during the dead zone, and the additional oscillation is very slight. Hundred kilohertz, the peak voltage is lower than 20V, the peak current is lower than 10, and the attenuation is very fast, which has no effect on the circuit operation, so in fact, in our case, the 0 buffer circuit can be no longer added.
For short-circuit overcurrent protection, according to the characteristics of 81, the protection off time is too long or too short. Although the driver M57959L has overcurrent detection and slow shutdown protection, its overcurrent detection response time is 10 old, which cannot protect against short pulse overcurrent. Therefore, we did not use the M57959L overcurrent detection function.
This function is implemented by an additional circuit to detect the current signal by the Hall sensor and remove the interference signal through filtering, and then compare the signal through the comparator, if an overcurrent occurs. Bay, maintain overcurrent 2 old adjustable lock, and high-speed optocoupler to set the M57959L overcurrent detection terminal to a high level, through the 55795 hole overcurrent slow turn-off function to achieve short pulse overcurrent protection.
6 Conclusion In the design of switching power supply, the rational selection of important devices is very important. Only a large number of tuning, research, mastering the parameter characteristics of various devices, and after a comprehensive and comprehensive trade-off, can rationally select the device. This article only describes the author's practical experience in the actual development of laser switching power supply. Due to space limitations, the selection of power supply circuit components will not be repeated.
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