Design of Laser Drive Power Supply Based on CPLD

1 Introduction

Laser processing mainly uses CO: laser beam to focus on the surface of the material to melt the material, while blowing the melted material with a compressed gas coaxial with the laser beam to complete the cutting of the desired trajectory pattern or the engraving of the corresponding handicraft surface. Laser processing belongs to non-contact processing, which has many advantages such as many processing methods, strong adaptability, high processing precision, good quality and high processing efficiency. As the direct control unit of the laser, the laser drive power supply has the highest frequency and optical power stability and reliability of the optical switch response, which will directly affect the final processing effect. Based on the requirements of fast response and light stability, Lechuang Automation Technology Co., Ltd. has developed a digital high-power laser driver power supply based on CPLD.

2 system composition and working principle

2.1 System composition

The system structure of digital high-power CO: laser driving power supply based on CPLD is shown in Figure 1. The system is mainly composed of main power supply, regulated power supply, auxiliary power supply, drive bridge, inverter boost, feedback circuit and digital control circuit. The main power supply and the regulated power supply mainly complete the stable output of the AC20V input to the 310V DC voltage, ensuring that the inverter boosting part works stably and reliably under a reasonable parameter. The auxiliary power supply mainly converts the 310V DC voltage into SV and 12V DC voltage for the digital control part and the feedback comparator part. The drive bridge and inverter boost are mainly required to complete the load of about 200 (edge ​​V high voltage output. The feedback circuit mainly plays a role in protection and controls the range of output current.

2.2 Working principle

In the schematic diagram of the laser driving power supply, the AC202V is rectified and filtered to generate a DC voltage of 310V. The 310V DC voltage is output through the regulated power supply. The stable 310V DC voltage is supplied to the inverter boosting part and the auxiliary power supply. The auxiliary power supply puts the 3lOV DC voltage. The 12V and SV DC voltages are supplied to the digital control section and the feedback section to provide a reference voltage. The digital control section performs power control by controlling the on-time of the drive bridge. The feedback circuit protects the output current from exceeding 30MA by sampling the current at the source.

3 function implementation

3. Main circuit and voltage regulator circuit

The AC220V is rectified and filtered to obtain a DC voltage of about 301V, and then a stable 3lOV DC voltage is obtained through the switching regulator power supply.

3.2 drive bridge and inverter boost section

The 31O V DC voltage is obtained by a half-bridge inverter to obtain a high-frequency square wave voltage. In order to ensure the low-current laser, a series resonance and a parallel resonance technique are employed in the inverter circuit. The boosting portion of the high frequency step-up transformer and the high voltage rectifier circuit is packaged as a separate component high voltage package. In the design, two high voltage packages are used in series to output power to the laser.

3.3 Digital control part and feedback part

The digital part is controlled by CPLD. On the one hand, CPLD completes the logic control of switching light, water protection, overcurrent and overvoltage feedback, etc. On the other hand, it mainly completes the output of PWM wave.

3.4 Auxiliary Power Section

Based on the auxiliary power supply of the VIPer22 A converter and the high-frequency power transformer, the output voltage waveform is stable without large spikes.

4 Features

4.1 good stability, strong resistance to external voltage fluctuations, large adjustment range

By designing a primary switching regulator power supply before the inverter boost circuit, the regulated power supply can ensure the voltage of the external network changes between 15% (187V) and +10% (242V). Part of the reference voltage is stable at 30v, which ensures that the inverter boosting part can work under a stable parameter and improve the stability of its work.

4.2 High frequency response

Because the control part adopts the digital control method based on CPLD, it can be used as the control pulse of lokb/s in laser engraving processing, which can complete the engraving of slope carving and small characters well.

4.3 Accurate power control

In the laser cutting process, since the duty ratio of the driving pulse outputted by the digital control module is not affected by the external non-control signal, stable power output under long-term operation can be ensured. In laser engraving, it can respond to the power data of the control system in real time. At the same time, because the laser output power and the working current are not linear, when the slope is engraved, the optical power can be corrected by the digital control part to make it linearly change. Ensure the slope requirements in the engraving slope.

4.4 Customizable control methods

In laser processing applications, there are sometimes many special processing requirements, such as the initial light output required for the cutting stage. The digital control method can easily modify the program to meet the corresponding new requirements.

5 Conclusion

By testing for a long time on a 1.6M laser produced by Chengdu Micro Technology Co., Ltd., the laser drive power supply has high frequency response, precise control, and small output current ripple, which can ensure long-term stable operation of the laser.

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