Development of a small-size and light-weight AC adaptor

提出了一种采用开关电容(SC)电路的小体积、轻重量的AC/DC适配器，只需使用电容器和IC开关即可实现电压转换，不需要线圈和变压器。暂态响应表明，该电路的励磁涌流不到传统SC电源的一半(参见日本IEICE，第6卷，第422-431页，1993年6月)。由于在传统的SC电源中，四个300μF电容器通过全波整流电路同时连接到一条商业电力线上，因此涌流变大。另一方面，该电路无需软启动电路即可抑制大的涌流，因为电荷转移电容值仅为30μF。然而，当商业电力线在半个周期内发生停电时，该电路不能保持额定负载的输出电压，因为输出的时间常数小于常规电路的1/7，即该电路的总电容约为180μF，而传统电路的总电容为1,200μF。该电路的电源块容易产生噪声，而控制块对噪声敏感，由于实验电路由分立元件组成，布线较长。因此，当输入电压较高时，控制电路可能会发生故障。实验验证还没有完成，虽然使用分立器件的电路工作正常，并通过HSPICE仿真获得了良好的特性，但为了防止控制电路的故障，未来将以除电容之外的IC形式实现所提出的电路，并验证实验特性。

In this research, a small-size and light-weight AC/DC adaptor using switched-capacitor (SC) circuit is presented which can carry out voltage conversion by using only capacitors and IC switches without using a coil and a transformer.The transient response showed that the inrush current of the proposed circuit is less than half of the conventional SC power supply (refer to the IEICE of Japan, vol.J76-C-II, no.6, pp.422-431, June 1993). Since in the conventional SC power supply, four 300μF capacitors are connected to a commercial power line simultaneously through a full wave rectifier circuit, the inrush current becomes large. On the other hand, in the proposed circuit the large inrush current can be suppressed without using a soft start circuit, since the value of the charge transfer capacitors is only 30μF. However, the proposed circuit can not keep the output voltage at the nominal load when a power failure is occurred during a half period of a commercial power line, because the time constant of the output is shorter than 1/7 of the conventional circuit, namely, the total capacitance of the proposed circuit is about 180μF and that of the conventional circuit is 1,200μF.The power supply block of the proposed circuit is easy to generate noise and the control block is sensitive for noise, since the experiment circuit is composed of discrete parts and its wiring is long. Therefore, a control circuit may malfunction when the input voltage is high. The verification by experiment is not finished yet.Although the circuit operations using discrete parts are verified normally by experiments and the excellent characteristics are obtained by Hspice simulations, in future, the proposed circuit will be implemented in an IC form except capacitors in order to prevent malfunction of the control circuit and the experimental characteristics will be verified.