| Switch mode power supply (SMPS) has advantages of high convert efficiency, small size, high control precision, which is widely applied in the field of consumable electronic product, communication, electricity, energy resource, aviation, military, etc. As the rapid development of information industry and wide application of portable electronic product, the domestic market of SMPS increased significantly, so SMPS has become the hotspot of the domestic power electronic research.Peak current control realizes the dual-loop control on the basis of voltage mode control by using current feedback, which can improve the stability and transient response performance of the system. Nowadays, the low- power SMPS in portable electronic product generally adopts this control technique. At present, pulse width modulation (PWM) is one of the most popular modulation mode applied in the SMPS, because in the condition of high load, it has advantages of high efficiency, high precision, and excellent ability of avoiding noise interference.Based on the application background mentioned above, at first, this thesis analyzes the circuit and system's characteristic of the peak current control PWM boost SMPS carefully, and then a novel circuit structure is presented in this thesis, which is used to predigest the cascade of error amplifier and PWM comparator used in the traditional SMPS control IC: sum-comparator. The sum-comparator can realize the dual-control which is composed of current inner loop and voltage outer loop in the peak current control system, and also can reduce the error and delay caused by the error amplifier in the traditional SMPS control IC. For this, it improves the speed and precision of PWM and enhances the transient response performance of the peak current control SMPS system. In addition, for optimizing the system's characteristic further, the Gm-C integrator is given to eliminate the steady state error in system and enhance the ability of load regulation.At the end of this thesis, a peak current control PWM boost SMPS control IC is presented, which is fabricated with 0.8μm BCD process and integrated with high precision voltage reference, OSC, Slope-compensation function circuit, current-sensing circuit, sum-comparator, Gm-C integrator and so on. The SMPS constructed by the control IC can work in different operations for choosing different external components to meet the demand of SMPS application. Besides, it also has some excellent characteristics, such as lower output ripple, high convert efficiency, well transient response performance and strong ability of load regulation. In the condition of typical application, the HSPICE simulation results show as follows: output voltage ripple is less than±1%, convert efficiency is up to 85%; When the load current step from 10mA to 100mA, the dynamic sag is only 0.8% and the restore time is 25μs; In addition, Gm-C integrator reduces the steady state error in system effectively. |
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