臭氧电源驱动保护电路的改进与实现

Improvement and Realization of Driving Protection Circuit in Power Supply of Ozonizer

针对大功率臭氧电源中采用EXB841直接驱动IGBT时所存在的负栅压不足、过流保护阈值太高、虚假过流以及过流无自锁等缺陷,提出了几点改进方法:用外接稳压管替代EXB841内部稳压管以提高负栅压;适当提高EXB841的电源电压,采用24V直流电源供电,并通过阈值检测电路实现过流阈值的精准和连续调节,以保证正向驱动电压;采用不对称的开启和关断方法,IGBT开通时栅极串接电阻较小,而IGBT关断时栅极串接电阻较大,从而使过电压减小,以改善控制脉冲的前后沿陡度和减少集电极尖脉冲;采用锁定保护电路以防止虚假过流并锁定过流。最后设计并测试了优化驱动电路。试验测试结果表明:该优化电路克服了原EXB841典型驱动电路的缺陷,极大地改善了IGBT的驱动与保护性能,具有实用价值。

In the high power supply of ozonizer, the chipset of EXB841 is usually adopted to drive and protect IGBT. But EXB841＇s directly driving IGBT has some shortcomings, such as the lower negative grid-voltage, the higher over-current protection threshold, the false over-current and the unlocked over-current. In the paper, the several improved methods are put forward. The inner regulation tube is replaced by the external regulation tube to increase the negative grid-voltage. At the same time, insuring the positive driving-voltage, it is proposed to adjust properly the isolated supply which provided the driving power with EXB841 to 24VDC. The threshold detection circuit is designed to realize the continuous exact regulation of the over-current threshold. The method of the anisomerous turn-on and turn-off is used to ameliorate the fore-and-aft edge gradient of the IGBT＇s driving pulse and decrease the sharp pulse of the collector. When IGBT is turned on, the grid series resistance is smaller. While IGBT is turned off, the grid series resistance is bigger to reduce the over-voltage. The locked protection circuit is utilized not only to avoid false over-current but also to lock the real over-current when the over-current appear. Finally the optimized driving circuit is designed and experimented. The experimental results show that the improved circuit overcomes the inherent lacks of the typical EXB841＇ driving circuit and improves greatly IGBT＇s driving and protection capability. So it possesses applied value.