Research And Design Of A Boost PWM Switch-Mode Power Supply Control Chip

The field of power electronics is concerned with the processing ofelectrical power using electronic devices. Switch-mode power supply(SMPS) is an important part of power electronics technology. Thedramatic decrease of size and cost of SMPS and the performanceimprovement in the recent years are promoting its extensiveapplications in industrial, commercial, residential, aerospace, militaryand utility environments. In today's customer market, battery-operatedportable electronics devices, such as notebooks, cellular phones andMP3 are in great demand. In order to decrease the size and weight ofthese devices, miniaturization of power modules is essential. Powermanagement ICs, such as highly efficiency, low voltage switch-modeDC-DC converters (SMPC), are mandatory in these devices formaximum the system run time. For voltage conversion performed bycustom-designed highly integrated converters with individual loads,the volume of the converters will typically be much smaller than thevolume of all batteries required achieving the equivalent extension ofrun time. Although the SMPS market in our country is very great, thedesign of SMPS is quite backward, especially in SMPC ICs. Thereforeit is extremely necessary to invest more strength in SMPC ICs.The core of SMPC is the power switching circuit. According tothe load to the power source requirement, SMPC takes charge of thefeedback control network to turn on or turn off the semiconductorswitching devices. In general, a switch-mode power converter containstwo blocks. One is the power circuit which takes charge of transferringand transforming the power to the loads. It contains only the electronicswitcher, inductor and capacitor. With different combination, we canacquire various type converters. The other is the complex controlcircuits which processes the control signals. With the development ofVLSI, the integrated circuits have taken places of the discretecomponents to realize the control block. Now the demand on highefficiency, high reliability and high precision and high power packagebecomes the design challenge to DC-DC ICs.The object of the paper is to design a high efficiency, highreliability, simply off-chip circuits Boost DC-DC power converter IC.According to whether the current of the inductor is continuous or not,there are two modes of the SMPS, continuous mode (CCM) anddiscontinuous mode (DCM). Considering power converter is aclose-loop system, I firstly researched and analyzed the whole system,including two modes' steady state and dynamic state analysis,choosing control mode and stability criteria, which instructed thedesign of power IC. During the analysis, I acquired the conditions tomake sure which working mode was selected.Because there are power switching devices, the DC-DC powerconverter is a nonlinear time-varied system and the linear controltheories could not be directly used to analyze the system. Therefore Ifirstly linearized the main control block with PWM Switch Mode andacquired its small signal equivalent circuits. Basing on the equivalentcircuits, we got the line-to-output and control-to-output transferfunctions. From these transfer functions, we learned that there was aright half-plane zero (RHP zero) in CCM. Due to the RHP zero, it wasdifficult to attain sufficient phase margin in the single loop feedbacksystem. In order to improve the reliability, it was necessary to greatlydecrease the gain of the error amplifier. In the view of that there wasno RHP zero in DCM, we designed the DC-DC power converter towork in DCM.In the thesis, some of the main functional modules wereresearched and designed, including bias current, reference voltage,oscillation, error amplifier, PWM comparator and soft-start circuit.Their topologies, schematics were introduced and developed. Throughthe careful designing of the operational amplifier in reference voltagemodule, I acquired a high reliability, low temperature coefficient, highPSRR reference voltage, which improved the output voltage precision.Although the structures of these modules were simple, they couldwork properly and efficiently in wide range of ambient temperaturesand supply voltage variations.On the basis of the system and circuit level design, the simulationperformed in the Hspice indicated successful operation. Thesimulation's results showed that this converter could operate from 160kHz to 400 kHz, with supply voltage from 1.5V to 3.8V, which wassuitable for single-cell battery supply application. The output ripplevoltage was about 30mV, the output precision was ± 1%, with a47uF off-chip capacitor and a 18uH off-chip inductor. The powerefficiency was over 80% for 5V output voltage and 100mA loadcurrent. The results indicated that it had met the design requirementsof high efficient, high precision and low supply voltage. The DC-DCconverter has been fabricated with a 0.5um N-well, 1P2M CMOSprocess.