| The power switch IC owns many factors, such as smart, intelligent, stable output, high efficient, easy to use. With the electronics’tend of smart and low power-consume, especially in consumer electronics, power switch IC becomes more and more popular.When the load changes, the power switch IC which we have designed can automatically change its current limit. Under PFM, the frequency of oscillator is proportional to system output voltage, with the aim to keep the output current stable. And using PSM decreases system power-consume when the system is in the standby or light load condition.Before the circuit design, the paper describes the power switch ICs factors, directions of research and typical basic working principle of fly-back converter. Then the paper proposes a PFM modulation mode AC-DC power switch IC with frequency jitter, the structure and working principle are introduced.When designing the cell of IC, we use theoretical analysis and math computing to accelerate design process. The reference is foundation for the IC to start working. It is basic, but most important. The protection method including over-temperature and over-current is considered in the paper. The paper’s key point is oscillator and its modulation. The frequency jitter and PFM modulation mode are related to oscillator. The frequency jitter can decrease the EMI, and frequency of oscillator will be changed under PFM modulation to reach constant-current output.After designing the cell of IC, the system simulation with HSPICE shows us that the functions of constant-current output and constant-voltage output work well.Layout links the circuit design and product. When designing the layout, we need pay attention to basic rules, such as layout symmetry, the current capacity, driving capability. DRC and LVS must have to be done through the layout process.The simulation result after layout suggests that the product reaches the design target. The work we have done is a worthy attempt in AC-DC power switch IC design. |
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