基于恒定导通时间的功率因数提高方法研究

发布时间：2018-12-06 07:49

【摘要】：随着电力电子技术的发展和创新,在稳压电源中,开关电源以其低功耗、高效率的优势很快的取代了线性稳压电源。但是在传统的降压型AC-DC开关电源的功率因数校正器中存在一个普遍的问题,输入电压是正弦交流信号,当输入电压小于输出电压的情况下,输入电流不再跟随输入电压的波形,输入的电流近似等于零,这个区间为死区,死区的出现使得功率因数的提高受到了很大影响。针对这一问题,本文利用一种新的功率因数校正技术,通过添加额外的辅助绕组和两个开关管对外围电路进行改善。改善后的电路会自动的根据输入电压与输出电压的关系,将电路的工作状态分为两个模式。在输入电压大于输出电压时,校正器会控制外围电路工作在降压型模式;在输入电压小于输出电压时,外围电路则工作在降压-升压模式,这样就可以消除因输入电压过小而存在的死区,输入电流也不再是零,并且可以跟随输入电压的波形。工作在降压-升压模式时,输入电流波形的调节,是通过系数K来完成的,K是校正器内部误差运放的输出端电压的分压系数,合理的调整系数K的大小,就能使输入电流在两个工作模式进行切换时完成良好的衔接,不会出现电流脉冲现象。消除了死区的校正器,我们再利用准谐振技术原理控制外部开关管的导通和关断,有效的降低外围电路功率管在导通时的能量损耗,设置合适的器件参数,可以让校正器的功率因数近似为1,并且外围电路中输入电流的高次谐波分量也能够很好的符合IEC61000-3-2中C类准则,减少对电网中电能的浪费。该方法是基于恒定导通时间模式的降压型变换器实现的,并且本文还对传统的恒定导通时间控制电路进行了改进和优化,用MOS管代替了充放电电容,根据输入电压自动的调节导通时间,不仅节约了芯片面积,还使导通时间的控制更为准确,去除了传统电路中存在的弊端。论文对研究的改进方法进行了全面的理论分析,并且借助Matlab软件对外围电路进行了理论验证,利用Cadence和Hspice等仿真工具对外围电路和控制电路的结合做了仿真,仿真结果表明,输入电流的波形得到了明显的改善,所设计的改善电路达到了预期的效果,消除了开关电源中的死区。
[Abstract]:With the development and innovation of power electronics technology, switching power supply (SMPs) has replaced linear power supply with its advantages of low power consumption and high efficiency. However, there is a common problem in the traditional power factor corrector of AC-DC switching power supply. The input voltage is sinusoidal AC signal, when the input voltage is less than the output voltage, The input current no longer follows the waveform of the input voltage, and the input current is approximately equal to zero, which is the dead zone. The rise of the power factor is greatly affected by the emergence of the dead-time. To solve this problem, a new power factor correction technique is used to improve the peripheral circuits by adding additional auxiliary windings and two switches. The improved circuit will be automatically divided into two modes according to the relationship between the input voltage and the output voltage. When the input voltage is larger than the output voltage, the corrector controls the peripheral circuit to work in the step-down mode. When the input voltage is less than the output voltage, the peripheral circuit works in the voltage-boost mode, which can eliminate the dead zone because the input voltage is too small, and the input current is no longer zero, and the waveform of the input voltage can be followed. The regulation of input current waveform is accomplished by coefficient K, which is the voltage partition coefficient of output terminal voltage of the internal error amplifier of the corrector, and the reasonable adjustment coefficient K, when working in the mode of step-down and boost voltage, the input current waveform is adjusted by the coefficient K, the output voltage of the output terminal voltage of the internal error amplifier of the corrector is adjusted reasonably. The input current can be connected well when switching between the two modes without the phenomenon of current pulse. The dead-time corrector is eliminated. We use the principle of quasi resonance technology to control the turn-on and turn-off of the external switch tube, effectively reduce the energy loss of the peripheral circuit power tube when it is on, and set the appropriate device parameters. The power factor of the corrector can be approximately 1, and the high harmonic component of the input current in the peripheral circuit can well conform to the C criterion in IEC61000-3-2, and reduce the waste of electric energy in the power network. This method is based on the constant on-time mode of the step-down converter, and this paper also improves and optimizes the traditional constant on-time control circuit, and uses MOS to replace the charge-discharge capacitor. According to the input voltage, adjusting the on-time automatically not only saves the area of the chip, but also makes the control of the on-time more accurate, and eliminates the disadvantages of the traditional circuit. This paper makes a comprehensive theoretical analysis of the improved methods, and verifies the peripheral circuits with the help of Matlab software. The combination of peripheral circuits and control circuits is simulated by Cadence and Hspice. The simulation results show that. The waveform of input current is improved obviously and the designed circuit achieves the desired effect and eliminates the dead time in the switching power supply.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM46

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