The present invention relates to a power supply for converting an AC input into DC power so as to supply the DC power to a load, and particularly relates to such a power supply having an uninterruptible function.
A communication/information appliance such as a disk array apparatus receives a commercial AC input, makes an AC/DC converter convert the AC input into a desired DC voltage required by a load in the appliance, and supplies the DC voltage to the load. In order to improve reliability of a power supply in the appliance, AC/DC converters are put in parallel redundant operation. Further, in order to improve reliability on the commercial AC, the inputs to the AC/DC converters are obtained from two AC systems. Further, in order to achieve high reliability on the commercial AC input, a power supply configuration provided with an uninterruptible power supply (hereinafter referred to as UPS) at the outside is used. A main circuit of the UPS connected is composed of an AC/DC converter, a battery, an inverter, and a change-over switch. Normally, the battery is charged while DC power is supplied to the inverter by the AC/DC converter, so that the DC power is converted into stable AC power by the inverter and the stable AC power is supplied to the communication/information appliance. When the AC input is interrupted, the DC power of the battery is converted into AC power by the inverter so that the AC power is supplied to the communication/information appliance. When a failure occurs in the inside of the UPS, power supply is changed to a bypass so that an AC input is supplied to the communication/information appliance directly. Incidentally, as a specific example of the aforementioned background art, there is a power supply described in JP-A-7-194118.
In the background-art power supply configuration, in a normal operation mode, there are two stages of power conversion in the inside of the UPS and a converter for converting AC power into DC power directly in the communication/information appliance side. That is, three stages of power conversion are required. Accordingly, conversion efficiency is worsened. Moreover, because the background-art power supply configuration is made so that a plurality of stages of converters having overlapping functions are connected, the volume of the power supply is large and the cost thereof is high. Further, with the advance of diversification of communication/information appliances, the power supply is, in most cases, formed to correspond to a wide-range input so that any appliance can be selected on the user side without awareness of an input voltage. When an external UPS is connected, there is, however, a problem that the UPS of an input voltage specification adapted to the user environment must be selected because the input/output voltage specification of the UPS is fixed.