| Summary: | 博士 === 國立交通大學 === 電機與控制工程系所 === 96 === This dissertation presents a novel CMOS charge pump circuits (CPCs) utilizing the pumping gain increase (PGI) circuits and the exponential-gain structure with high voltage transfer efficiency to generate boosted output voltages. By employing the PGI circuits, the threshold voltage problem of the MOSFET used as a switch is solved and the limitation of the diode-configured output stage is removed. Thus the boosted output voltage increases more linearly versus the pumping stage number. For the further application of the PGI circuits, an exponential-gain structure is also presented. By using this structure, fewer voltage pump stages are needed to obtain the required output voltage. For 1.5 V supply voltage operation, the simulation and experimental results show that the proposed designs would have good pumping efficiency with a low input supply such as one battery cell.
In addition, thorough analysis and a complete equivalent model of the PGI circuit with a resistive load are proposed. Based on the simple analytical model, the characteristics of the PGI circuit can be approximately predicted and the simple equations, which are useful for a pencil and paper design with an acceptable safety margin, can also be found for planning the desired circuit performance in the steady state. Furthermore, an optimized method of the PGI circuit for a resistive load is developed in terms of the stage number and the ratio between pump capacitors as optimization criterions. For 1.5 V supply voltage operation, reliability and accuracy are demonstrated by comparisons between SPICE simulations of the PGI circuit and the corresponding results from the equivalent model. The model also has been validated by means of measurement taken from a test chip, and typically the relative errors are lower than 5 %. Finally, although the derivation of the model was based on PGI circuits, the design strategy can also be equally valid for any other improved CPC designs which are able to eliminate voltage drops within the inner stages and the output stage.
Finally, a design procedure of a charge pump regulator based on the equivalent model is illustrated with a design example. The presented charge pump regulator adopts the automatic pumping frequency scheme including a voltage-controlled oscillator, a charge pump circuit, an error detector, and a compensator. By employing the equivalent model, this regulator with a frequency compensation scheme can be implemented and all of the characteristics can be designed through manual and/or computer analysis. The final regulator provides a negative feedback to the pump operation and would insure the output voltage against the variations of loading conditions. From the design example, the accuracy has been demonstrated by comparing the simulation results between the equivalent regulator model and the practical regulator. The primary advantage of this modeling approach is the ease by which the regulator system can be analyzed. This permits that a fast charge pump regulator design would work in practice.
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