Loop Modeling And Research Of BUCK Converter

From the late fifties of the last century, the power electronics technology were developed rapidly, especially in the switch power supply (Switch Mode Power Supplies, SMPS). Switching power supplied with high efficiency, small size, easy to carry and widely used in LED lighting, mobile power, power electronics, and aerospace and so on. However, for the switching power supply input voltage disturbance, output load disturbance likely to cause mutation system output voltage overshoot greater stability and other issues, this has been a lot of power engineers and power electronics research staff attention problems.Aiming at the above problems, it introduced the research status of switch power supply, and BUCK converter, for example, analyzed and derived works BUCK converter; simultaneous analysis of continuous conduction mode and discontinuous conduction mode boundary conduction several relational model of steady-state operating mode. After studying BUCK converter modulation modes, including hysteresis control, voltage control and current control.This paper binded the Dr. R Ridley model, and establisheda detailed derivation of peak current mode control BUCK converter’s complete mathematical model. Established a large-signal and small signal model of the system model and through the small-signal model deriving the BUCK converter power stage and loop transfer function. Selected a different type of error amplifier to compensate for the system, which mainly including:type Ⅰ,Ⅱ,Ⅲ common operational amplifier, type Ⅱ and type Ⅲ and transconductance operational amplifier compensation network. And the output voltage to the control voltage transfer function was derived and analyzed its pole-zero conditions.The results showed that when the error amplifier OPA type of op amp, although type Ⅲ compensation network in the region with broadband more than type Ⅱ compensation network introduces a right half-plane zero to increase the phase margin of the system. However, when the output load resistance is too low, the gain margin of the system is insufficient, crossover frequency very close to one-half the switching frequency, so that the compensation effect of the system was not obvious. To this end, we designed an improved compensation network before type Ⅱ compensation network increase adjustable resistance, to improve the crossover frequency was closed to one-half the switching frequency caused by insufficient phase margin issue. When the error amplifier OTA type of op amp, type II and type III compensation network were able to provide at least one each of poles and zeros, in practice, often crossing the zero setting within the frequency so that the input voltage or output load disturbance occurs changes sometimes cause crossover frequency changes.For less than the error amplifier compensation link compensation, the paper designed a new type of variable parameters proportional-integraland disturbance observeromposite control strategy to address the input voltage disturbances and output load voltage output caused by mutations in a huge overshoot problems. Simulation results showed that this method can effectively suppress the interference system, good anti-jamming performance.